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1 
MATHS PROJECT 
Rachna Nathawat 
Class IXth-c 
Roll no. 29
2 
Math 131 - Chapter 2 
Linear Equations, Inequalities, and 
Applications 
• 2-1 Linear Equations in One Variable 
• 2-2 Formulae 
• 2-3 Applications 
• 2-5 Linear Inequalities in One Variable
3 
2-1 Linear Equations in One Variable 
A linear equation in one variable can be 
written in the form Ax + B = C, where A,B, 
and C are real numbers with A  0. 
• Example 1: x + 4 = -2 
Note: x + 4 by itself is called an algebraic expression. 
• Example 2: 2k + 5 = 10 
Note: A linear equation is also called a first degree equation since the 
highest power of x is 1. 
• The following are called non-linear equations: 
y = 3x2 +10 x  2
4 
2-1 Linear Equations in One Variable 
Decide whether a number is a solution of 
a linear equation. 
• Example 3: 8 is a solution of the equation x – 3 = 5 
An equation is solved by finding its “solution set”. 
The solution set of x – 3 = 5 is {8}. 
Note: Equivalent equations are equations that have the same 
solution set: 
• Example 4: 5x +2 = 17, 5x =15 and x =3 are equivalent. 
The solution set is {3}.
5 
2-1 Linear Equations in One Variable 
Addition Properties of Equality 
• For all real numbers A,B, and C, the 
equations A = B and A + C = B + C are 
equivalent. 
Note: The same number can be added to each side of an expression 
without changing its solution set. 
• Example 5: Solution of the equation x – 3 = 5 
x – 3 +3 = 5 + 3 
x = 8 
The solution set of x – 3 = 5 is {8}. 
• Example 6: 5x +2 = 17, 5x + 2 + (-2) =17 + (-2) and 5x =15 
are equivalent. 
The solution set is {3}.
6 
2-1 Linear Equations in One Variable 
Multiplication Properties of Equality 
• For all real numbers A,B, and for 
C  0, the equations A = B and AC = BC 
are equivalent. 
Note: Each side of an equation may be multiplied by the same non-zero 
number without changing its solution set. 
• Example 7: Solution of the equation 
The solution set of 5x = 15 is {3}. 
5x = 15 
1 1 
( ) 5 x  
( ) 15 
5 5 
x = 3
7 
2-1 Linear Equations in One Variable 
Example 8: Solve: -7 + 3x – 9x = 12x -5 
-7 + 7 –6x = 12x –5 + 7 
-6x –12x = 12x –12x +2 
-18x = 2 
1 1 
 x   
( ) (-18) ( ) 2 
18 18 
1 
x = - 
9 
1 
- 
9 
The solution set is { }.
8 
2-1 Linear Equations in One Variable 
Solving a Linear Equation in One 
Variable: 
• Step 1: Clear fractions. (Eliminate any fractions by multiplying 
each side by the least common denominator.) 
• Step 2: Simplify each side separately. (Use the distributive 
property to clear parenthesis and combine like terms.) 
• Step 3: Isolate the variable terms on the left side of the equal 
sign. (Use the addition property to get all the variable terms on 
the left side and all the numbers on the right side.) 
• Step 4: Isolate the variable. (Use the multiplication property to 
get an equation where the coefficient of the variable is 1.) 
• Step 5: Check. (Substitute the proposed solution into the original 
equation and verify both sides of the equal sign are equivalent.)
9 
2-1 Linear Equations in One Variable 
Example 8: Solve: 6 – (4 +x) = 8x – 2(3x + 5) 
Step 1: Does not apply 
Step 2: 6 – 4 –x = 8x – 6x –10 
-x +2 = 2x – 10 
Step 3: -x + (-2x) +2 +(-2) = 2x + (-2x) –10 + (-2) 
-3x = -12 
Step 4: 
1 1 
 x   
( ) (-3) ( ) (-12) 
3 3 
Step 5: 6 – (4 + 4) = 8(4) – 2(3(4) + 5) 
6 – 8 = 32 - 34 
-2 = -2 
The solution set is {4}. 
x = 4
10 
2-1 Linear Equations in One Variable 
Example 9: Solve: 
Step 1: 
Step 2: 
Step 3: 
Step 4: 
x x 
  
  
x x 
  
  
x x 
  
  
x   x 
  
Step 5: 
The solution set is {-1}. 
1 3 1 
2 4 2 
1 3 1 
4( ) 4( ) 
2 4 2 
1 3 1 
4( ) 4( ) 4( ) 
2 4 2 
2( 1) ( 3) 2 
x x 
2  2   3  
2 
3 5 2 
  
3  5  (  5)  2  (  
5) 
3 3 
x 
x 
x 
  
1 1 
( ) 3 ( )( 3) 
3 3 
1 
x 
x 
1 1 1 3 1 2 1 1 1 
: 
2 4 2 4 2 2 2 
Check 
  
  
    
   
11 
2-1 Linear Equations in One Variable 
Identification of 
Conditional Equations, 
Contradictions, and 
Identities 
• Some equations that 
appear to be linear 
have no solutions, while 
others have an infinite 
number of solutions. 
Note: Identification 
requires knowledge of 
the information in the 
table. 
Type of 
Equation 
Number of 
Solutions 
Indication 
when solving 
Conditional One Final line is: 
x = a number 
Contradiction None; 
solution set 0 
or null 
Final line is 
false, such as 
0=1 
Identity Infinite; 
solution set 
is all real 
numbers 
Final line is 
true, such as 
0=0
12 
2-1 Linear Equations in One Variable 
Example 9: Solve each equation, Decide whether it is conditional, 
identity, or contradiction. 
A) 5x – 9 = 4(x-3) 
5x – 9 = 4x –12 
x = -3  conditional 
The solution set is {-3} 
B) 5x –15 = 5(x-3) 
5x – 15 = 5x –15 
0 = 0  identity 
The solution set is {all real numbers} 
C) 5x –15 = 5(x-4) 
5x – 15 = 5x –20 
0 = -5  contradiction 
The solution set is {} or 0 (null set)
13 
2-2 Formulae 
A “mathematical model” is an equation or inequality that 
describes a real situation. Models for many applied problems 
already exist and are called “formulas”. 
A “formula” is a mathematical equation in which variables 
are used to describe a relationship. 
Common formulae that will be used are: 
d = rt distance = (rate)(time) 
I = prt Interest = (principal)(rate)(time) 
P = 2L + 2 W Perimeter = 2(Length) + 2(Width) 
amount 
percent percent 
 100%   100% 
 
base 
a 
b 
Additional formulae are included on the inside covers of your text.
14 
2-2 Formulae 
Solving for a specified variable: 
Step 1: Get all terms containing the specified variable on 
the left side of the equal sign and all other terms on the 
right side. 
Step 2: If necessary, use the distributive property to 
combine the terms with the specified variable. 
Step 3: Isolate the variable. (Use the multiplication (division) 
property to get an equation where the coefficient of the variable 
is 1.) 
• Example 1: Solve m = 2k + 3b for k 
2k = m –3b 
k = (m – 3b)/2
15 
2-2 Formulae 
• Example 2: Solve 
• Example 3: Solve 
1 
( 3) for 
2 
y  x  x 
1 3 
( ) 
2 2 
y x 
  
1 3 
( x ) 
 y 
 
2 2 
1 3 
x y 
2( ( )) 2( ) 
  
2 2 
2 3 
x y 
  
A  2HW  2LW  2LH for W 
2 HW 2 LW A 2 
LH 
W (2 H 2 L ) A 2 
LH 
   
   
A  
LH 
( 2 ) 
(2 2 ) 
W 
H L 
 

16 
2-2 Formulae 
• Example 4: Given a distance of 500 miles and a rate (speed) 
of 25 mph, find the time for the trip. 
d rt solve for t 
rt d 
d 
d miles 
t    
hours 
r miles 
• Example 5: A 20 oz mixture of gasoline and oil contains 1 
oz of oil. What percent of the mixture is oil? 
t 
r 
 
 
 
500 
20 
25 
hour 
100% 
amount 
percent 
base 
  
1 
100% .05 100% 5% 
20 
   
17 
2-3 Applications of Linear Equations 
Translating words to mathematical 
expressions. 
Note: There are usually key words or phrases that translate into 
mathematical expressions. 
Translating from Words to Mathematical Expressions 
x and y represent numbers 
Verbal Expression Mathematical Expression 
Additions 
The sum of a number and 7 x + 7 
6 more than a number x + 6 
3 plus a number 3 + x 
24 added to a number x + 24 
A number increased by 5 x + 5 
The sum of two numbers x + y
18 
2-3 Applications of Linear Equations 
Translating words to mathematical 
expressions. 
Note: There are usually key words or phrases that translate into 
mathematical expressions. 
Translating from Words to Mathematical Expressions 
x and y represent the numbers 
Verbal Expression Mathematical Expression 
Subtractions 
2 less than a number x - 2 
3 minus a number 3 - x 
A number decreased by 5 x - 5 
A number subtracted from 10 10 - x 
The difference between two numbers x - y
19 
2-3 Applications of Linear Equations 
Translating words to mathematical 
expressions. 
Note: There are usually key words or phrases that translate into 
mathematical expressions. 
Translating from Words to Mathematical Expressions 
x and y represent the numbers 
Verbal Expression Mathematical Expression 
Multiplication 
2 times a number 2  x or 2x 
A number multiplied by 6 x  6 or 6x 
2 
of a number 
3 
2 2 
 
x or x 
3 3 
Twice a number 2  x or 2x 
The product of two numbers x  y or xy
20 
2-3 Applications of Linear Equations 
Translating words in to equations. 
Note: The symbol for equality, = , is often indicated by the word “is”. 
Translating from Words to Mathematical Equations 
Verbal Sentence Mathematical Equation 
Twice a number, decreased by 3, is 42 2 x - 3 = 42 
The product of a number and 12, 
decreased by 7, is 105 12x - 7 = 105 
The quotient of a number and the number 
plus 4 is 28 
The quotient of a number and 4, plus 
the number, is 10 
28 
4 
x 
x 
 
 
x 
x 
10 
4
21 
2-3 Applications of Linear Equations 
Distinguishing between expressions and 
equations. 
Note: An expression is a phrase. An equation includes the = symbol 
and translates the sentence. 
• Example 1: Decide whether each is an expression or an equation. 
A) 5x – 3(x+2) = 7 Equation 
B) 5x – 3(x+2) Expression
22 
2-3 Applications of Linear Equations 
Solving Applied Problems. 
Note: The following six steps are useful in developing a 
technique for solving applied problems. 
• Step 1: Read the problem carefully until you understand what 
is given and what is to be found. 
• Step 2: Assign a variable to represent the unknown value, using 
diagrams or tables as needed. 
• Step 3: Write an equation using the variable expressions. 
• Step 4: Solve the equation. (Isolate the variable on the left side of 
the equals sign) 
• Step 5: State the answer with appropriate units. (Does it seem 
reasonable?) 
• Step 6: Check the answer.
23 
2-3 Applications of Linear Equations 
Solving Applied Problems. 
At the end of the 1999 baseball season, Sammy Sosa and Mark 
McGwire had a lifetime total of 858 homeruns. McGwire had 186 
more than Sosa. How many runs did each player have? 
• Step 1: Total runs = 858 Sosa has 186 less than McGwire 
• Step 2: Let x = Sosa’s runs, then x + 186 = McGwire’s runs 
• Step 3: x + (x + 186) = 858 
• Step 4: 2x + 186 = 858 
2x = 672 
x = 336 x + 186 = 522 
• Step 5: Sosa had 336 homeruns. McGwire had 522 homeruns. 
• Step 6: 336 + 522 = 858 
858 = 858 
Checked:
24 
2-3 Applications of Linear Equations 
Solving Applied Problems. 
A woman has $34,000 to invest. She invests some at 17% and the 
balance at 20%. Her total annual interest income is $6425. Find the 
amount invested at each rate. 
• Step 1: Total investment = $34,000 Total interest earned is $6245 
• Step 2: Let x = amount at 17%, then $34,000 - x = amount at 20% 
• Step 3: .17x + .20(34,000 - x) = 6245 
• Step 4: .17x + 6800 - .20x = 6245 
-.03x = -555 
x = 18,500 34,000 – 18,500 = 15,500 
• Step 5: $18,500 invested at 17% $15,500 invested at 20% 
• Step 6: .17(18,500) + .20(15,5000 = 6245 
3145 + 3100 = 6245 
6245 = 6245 
Checked:
25 
2-3 Applications of Linear Equations 
Solving Applied Problems. 
How many pounds of candy worth $8 per lb should be mixed with 100 
lb of candy worth $4 per lb to get a mixture that can be sold for $7 per 
lb? 
• Step 1: Total mixture should sell for $7/lb. Given 100 lbs at $4/lb and 
an unknown amount at $8/lb. 
• Step 2: Let x = amount at $8 then x + 100 should sell at $7/lb 
• Step 3: 8x + 4(100) = 7(x + 100) 
• Step 4: 8x + 400 = 7x + 700 
x = 300 
• Step 5: 300 lb at $8/lb 
• Step 6: 8(300) + 4(100) = 7(300 + 100) 
2400 + 400 = 7(400) 
2800 = 2800 
Checked:
26 
2-3 Applications of Linear Equations 
Solving Applied Problems. 
How much water must be added to 20 L of 50% antifreeze solution to 
reduce it to a 40% antifreeze solution? 
• Step 1: Total mixture should be 40% antifreeze. Given 20 L at 50% 
produces 10 L of water and 10 L of antifreeze. Add an unknown 
amount of water. 
• Step 2: Let x = amount of water added, then x + 10 will be the water in 
the final solution and the amount of antifreeze is 10 L. 
• Step 3: 
• Step 4: 
amount 
percent percent 
 100%   100% 
 
base 
a 
b 
10 L of antifreeze 
 100%  
40 
10 L of antifreeze + (x+10) of water 
1000  40(10  (  
10)) 
1000  400  40  
400 
40  
200 
5 
x 
x 
x 
x 
 
10 L of antifreeze 
• Step 5: 5 L of water 
• Step 6: Check: 
100% 40% 
10 L of antifreeze + (5+10) of water 
10 
100% 40% 
25 
40% 40% 
  
  

27 
2-5 Linear Inequalities in One Variable 
Interval Notation is used to write solution sets of 
inequalities. 
Note: A parenthesis is used to indicate an endpoint in not included. A 
square bracket indicates the endpoint is included. 
Interval Notation 
Type of Interval Set Interval Notation Graph 
{x a  x } (a, ) 
{x  a  x  b} (a, b) 
{x  x  b} (-, b) 
{x  x is a real number} (-, ) 
Open Interval 
( 
a 
) 
b 
( 
a 
) 
b
28 
2-5 Linear Inequalities in One Variable 
Interval Notation is used to write solution sets of 
inequalities. 
Note: A parenthesis is used to indicate an endpoint in not included. A 
square bracket indicates the endpoint is included. 
Interval Notation 
Type of Interval Set Interval Notation Graph 
{x a  x} [a, ) 
{x  a  x  b} (a, b] 
{x  a  x  b} [a, b) 
{x  x  b} (-, b] 
Half-open 
Interval 
[ 
a 
] 
b 
] 
b 
( 
a 
) 
b 
[ 
a
29 
2-5 Linear Inequalities in One Variable 
Interval Notation is used to write solution sets of 
inequalities. 
Note: A parenthesis is used to indicate an endpoint in not included. A 
square bracket indicates the endpoint is included. 
Interval Notation 
Type of Interval Set Interval Notation Graph 
Closed Interval {x a  x  b} [a, b] 
] 
b 
[ 
a
30 
2-5 Linear Inequalities in One Variable 
A linear inequality in on variable can be 
written in the form Ax + B = C, where A, B, 
and C are real numbers with A  0. 
Note: The next examples include definitions and rules for < , >, 
, and  . 
• Examples of linear inequalities: 
x + 5 < 2 x – 3 > 5 2k +4  10
31 
2-5 Linear Inequalities in One Variable 
Solving linear inequalities using the Addition Property: 
For all real numbers A, B, and C, the inequalities A < B and 
A + C < B + Ca are equivalent. 
Note: As with equations, the addition property can be used to 
add negative values or to subtract the same number from each 
side . 
• Example 1: Solve k – 5 > 1 
k – 5 +5 > 1 + 5 
k > 6 
Solution set: (6,) 
• Example 2: Solve 5x + 3  4x – 1 and graph the solution set. 
5x – 4x  -1 –3 
x  -4 
Solution set: [-4,) 
[ 
-4
32 
2-5 Linear Inequalities in One Variable 
Solving linear inequalities using the Multiplication Property: 
For all real numbers A, B, and C, with C  0 , 
1) if C > 0, then the inequalities A < B and AC < BC are equivalent. 
2) if C < 0, then the inequalities A < B and AC > BC are equivalent. 
Note: Multiplying or Dividing by a negative number requires the 
inequality sign be reversed. 
• Example 1: Solve -2x < 10 
x > -5 
Solution set: (-5,) 
• Example 2: Solve 2x < -10 
x < -5 
Solution set: (-,-5) 
Note: The first example requires a symbol change because both sides 
are multiplied by (-1/2). The second example does not because both 
sides are multiplied by (1/2)
33 
2-5 Linear Inequalities in One Variable 
Solving linear inequalities using the Multiplication 
Property: 
• Example 3: Solve –9m < -81 and graph the solution set 
m > 9 
Solution set: (9, ) ( 
9
34 
2-5 Linear Inequalities in One Variable 
Solving a Linear Inequality: 
Step 1: Simplify each side separately. If necessary, use the distributive 
property to clear parenthesis and combine like terms. 
Step 2: Use the addition property to get all terms containing the 
specified variable on the left side of the inequality sign and all other 
terms on the right side. 
Step 3: Isolate the variable. (Use the multiplication (division) property 
to get an inequality where the coefficient of the variable is 1.) 
• Example 4: Solve 6(x-1) + 3x  -x –3(x + 2) and graph the solution set 
Step 1: 6x-6 + 3x  -x –3x – 6 
9x - 6  –4x – 6 
Step 2: 13x  0 
Step 3: x  0 
Solution set: [0, ) 
[ 
0
35 
2-5 Linear Inequalities in One Variable 
Solving a Linear Inequality: 
• Example 5: Solve and graph the 
solution set 
Step 1: 
Step 2: 
Step 3: 
1 3 
( 3) 2 ( 8) 
4 4 
Solution set: [ , ) 
m   m 
m m 
m m 
[ 
-13/2 
1 3 3 
2 6 
4 4 4 
1 11 3 24 
4 4 4 4 
1 3 24 11 
m m 
4 4 4 4 
2 13 
4 4 
13 
2 
m 
m 
    
   
   
  
  
13 
2 

36 
2-5 Linear Inequalities in One Variable 
Solving applied problems using linear inequalities: 
• Example 6: Solve 5 < 3x – 4 < 9 and graph the solution set 
5 + 4 < 3x < 9 + 4 
9 < 3x < 13 
3 < x < (13/3) 
Solution set: ( 3, ) 13 
2 ) ( 
3 13 
2
37 
2-5 Linear Inequalities in One Variable 
Solving applied problems using linear inequalities: 
Note: Expressions for inequalities sometimes appear as indicated in the table: 
Word Expression Interpretation 
• Example 7: Teresa has been saving dimes and nickels. She has three 
times as many nickels as dimes and she has at least 48 coins. What is 
the smallest number of nickels she might have? 
Let: x equal the number of dimes 
Then: 3x is the number of nickels 
and: 3x + x  48 
4x  48 
x  12  36 nickels 
a is at least b 
a is no less than b 
a is at most b 
a is no more than b 
a  b 
a  b 
a  b 
a  b
38 
2-5 Linear Inequalities in One Variable 
Solving applied problems using linear inequalities: 
• Example 8: Michael has scores of 92, 90, and 84 on his first 
three tests. What score must he get on the 4th test in order 
to maintain an average of at least 90? 
Let: x equal the 4th score 
92 90 84 
: 90 
4 
266 
90 
4 
266 360 
360 266 
94 
x 
Then 
x 
x 
x 
x 
   
 
 
 
  
  


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Linear equations inequalities and applications

  • 1. 1 MATHS PROJECT Rachna Nathawat Class IXth-c Roll no. 29
  • 2. 2 Math 131 - Chapter 2 Linear Equations, Inequalities, and Applications • 2-1 Linear Equations in One Variable • 2-2 Formulae • 2-3 Applications • 2-5 Linear Inequalities in One Variable
  • 3. 3 2-1 Linear Equations in One Variable A linear equation in one variable can be written in the form Ax + B = C, where A,B, and C are real numbers with A  0. • Example 1: x + 4 = -2 Note: x + 4 by itself is called an algebraic expression. • Example 2: 2k + 5 = 10 Note: A linear equation is also called a first degree equation since the highest power of x is 1. • The following are called non-linear equations: y = 3x2 +10 x  2
  • 4. 4 2-1 Linear Equations in One Variable Decide whether a number is a solution of a linear equation. • Example 3: 8 is a solution of the equation x – 3 = 5 An equation is solved by finding its “solution set”. The solution set of x – 3 = 5 is {8}. Note: Equivalent equations are equations that have the same solution set: • Example 4: 5x +2 = 17, 5x =15 and x =3 are equivalent. The solution set is {3}.
  • 5. 5 2-1 Linear Equations in One Variable Addition Properties of Equality • For all real numbers A,B, and C, the equations A = B and A + C = B + C are equivalent. Note: The same number can be added to each side of an expression without changing its solution set. • Example 5: Solution of the equation x – 3 = 5 x – 3 +3 = 5 + 3 x = 8 The solution set of x – 3 = 5 is {8}. • Example 6: 5x +2 = 17, 5x + 2 + (-2) =17 + (-2) and 5x =15 are equivalent. The solution set is {3}.
  • 6. 6 2-1 Linear Equations in One Variable Multiplication Properties of Equality • For all real numbers A,B, and for C  0, the equations A = B and AC = BC are equivalent. Note: Each side of an equation may be multiplied by the same non-zero number without changing its solution set. • Example 7: Solution of the equation The solution set of 5x = 15 is {3}. 5x = 15 1 1 ( ) 5 x  ( ) 15 5 5 x = 3
  • 7. 7 2-1 Linear Equations in One Variable Example 8: Solve: -7 + 3x – 9x = 12x -5 -7 + 7 –6x = 12x –5 + 7 -6x –12x = 12x –12x +2 -18x = 2 1 1  x   ( ) (-18) ( ) 2 18 18 1 x = - 9 1 - 9 The solution set is { }.
  • 8. 8 2-1 Linear Equations in One Variable Solving a Linear Equation in One Variable: • Step 1: Clear fractions. (Eliminate any fractions by multiplying each side by the least common denominator.) • Step 2: Simplify each side separately. (Use the distributive property to clear parenthesis and combine like terms.) • Step 3: Isolate the variable terms on the left side of the equal sign. (Use the addition property to get all the variable terms on the left side and all the numbers on the right side.) • Step 4: Isolate the variable. (Use the multiplication property to get an equation where the coefficient of the variable is 1.) • Step 5: Check. (Substitute the proposed solution into the original equation and verify both sides of the equal sign are equivalent.)
  • 9. 9 2-1 Linear Equations in One Variable Example 8: Solve: 6 – (4 +x) = 8x – 2(3x + 5) Step 1: Does not apply Step 2: 6 – 4 –x = 8x – 6x –10 -x +2 = 2x – 10 Step 3: -x + (-2x) +2 +(-2) = 2x + (-2x) –10 + (-2) -3x = -12 Step 4: 1 1  x   ( ) (-3) ( ) (-12) 3 3 Step 5: 6 – (4 + 4) = 8(4) – 2(3(4) + 5) 6 – 8 = 32 - 34 -2 = -2 The solution set is {4}. x = 4
  • 10. 10 2-1 Linear Equations in One Variable Example 9: Solve: Step 1: Step 2: Step 3: Step 4: x x     x x     x x     x   x   Step 5: The solution set is {-1}. 1 3 1 2 4 2 1 3 1 4( ) 4( ) 2 4 2 1 3 1 4( ) 4( ) 4( ) 2 4 2 2( 1) ( 3) 2 x x 2  2   3  2 3 5 2   3  5  (  5)  2  (  5) 3 3 x x x   1 1 ( ) 3 ( )( 3) 3 3 1 x x 1 1 1 3 1 2 1 1 1 : 2 4 2 4 2 2 2 Check            
  • 11. 11 2-1 Linear Equations in One Variable Identification of Conditional Equations, Contradictions, and Identities • Some equations that appear to be linear have no solutions, while others have an infinite number of solutions. Note: Identification requires knowledge of the information in the table. Type of Equation Number of Solutions Indication when solving Conditional One Final line is: x = a number Contradiction None; solution set 0 or null Final line is false, such as 0=1 Identity Infinite; solution set is all real numbers Final line is true, such as 0=0
  • 12. 12 2-1 Linear Equations in One Variable Example 9: Solve each equation, Decide whether it is conditional, identity, or contradiction. A) 5x – 9 = 4(x-3) 5x – 9 = 4x –12 x = -3  conditional The solution set is {-3} B) 5x –15 = 5(x-3) 5x – 15 = 5x –15 0 = 0  identity The solution set is {all real numbers} C) 5x –15 = 5(x-4) 5x – 15 = 5x –20 0 = -5  contradiction The solution set is {} or 0 (null set)
  • 13. 13 2-2 Formulae A “mathematical model” is an equation or inequality that describes a real situation. Models for many applied problems already exist and are called “formulas”. A “formula” is a mathematical equation in which variables are used to describe a relationship. Common formulae that will be used are: d = rt distance = (rate)(time) I = prt Interest = (principal)(rate)(time) P = 2L + 2 W Perimeter = 2(Length) + 2(Width) amount percent percent  100%   100%  base a b Additional formulae are included on the inside covers of your text.
  • 14. 14 2-2 Formulae Solving for a specified variable: Step 1: Get all terms containing the specified variable on the left side of the equal sign and all other terms on the right side. Step 2: If necessary, use the distributive property to combine the terms with the specified variable. Step 3: Isolate the variable. (Use the multiplication (division) property to get an equation where the coefficient of the variable is 1.) • Example 1: Solve m = 2k + 3b for k 2k = m –3b k = (m – 3b)/2
  • 15. 15 2-2 Formulae • Example 2: Solve • Example 3: Solve 1 ( 3) for 2 y  x  x 1 3 ( ) 2 2 y x   1 3 ( x )  y  2 2 1 3 x y 2( ( )) 2( )   2 2 2 3 x y   A  2HW  2LW  2LH for W 2 HW 2 LW A 2 LH W (2 H 2 L ) A 2 LH       A  LH ( 2 ) (2 2 ) W H L  
  • 16. 16 2-2 Formulae • Example 4: Given a distance of 500 miles and a rate (speed) of 25 mph, find the time for the trip. d rt solve for t rt d d d miles t    hours r miles • Example 5: A 20 oz mixture of gasoline and oil contains 1 oz of oil. What percent of the mixture is oil? t r    500 20 25 hour 100% amount percent base   1 100% .05 100% 5% 20    
  • 17. 17 2-3 Applications of Linear Equations Translating words to mathematical expressions. Note: There are usually key words or phrases that translate into mathematical expressions. Translating from Words to Mathematical Expressions x and y represent numbers Verbal Expression Mathematical Expression Additions The sum of a number and 7 x + 7 6 more than a number x + 6 3 plus a number 3 + x 24 added to a number x + 24 A number increased by 5 x + 5 The sum of two numbers x + y
  • 18. 18 2-3 Applications of Linear Equations Translating words to mathematical expressions. Note: There are usually key words or phrases that translate into mathematical expressions. Translating from Words to Mathematical Expressions x and y represent the numbers Verbal Expression Mathematical Expression Subtractions 2 less than a number x - 2 3 minus a number 3 - x A number decreased by 5 x - 5 A number subtracted from 10 10 - x The difference between two numbers x - y
  • 19. 19 2-3 Applications of Linear Equations Translating words to mathematical expressions. Note: There are usually key words or phrases that translate into mathematical expressions. Translating from Words to Mathematical Expressions x and y represent the numbers Verbal Expression Mathematical Expression Multiplication 2 times a number 2  x or 2x A number multiplied by 6 x  6 or 6x 2 of a number 3 2 2  x or x 3 3 Twice a number 2  x or 2x The product of two numbers x  y or xy
  • 20. 20 2-3 Applications of Linear Equations Translating words in to equations. Note: The symbol for equality, = , is often indicated by the word “is”. Translating from Words to Mathematical Equations Verbal Sentence Mathematical Equation Twice a number, decreased by 3, is 42 2 x - 3 = 42 The product of a number and 12, decreased by 7, is 105 12x - 7 = 105 The quotient of a number and the number plus 4 is 28 The quotient of a number and 4, plus the number, is 10 28 4 x x   x x 10 4
  • 21. 21 2-3 Applications of Linear Equations Distinguishing between expressions and equations. Note: An expression is a phrase. An equation includes the = symbol and translates the sentence. • Example 1: Decide whether each is an expression or an equation. A) 5x – 3(x+2) = 7 Equation B) 5x – 3(x+2) Expression
  • 22. 22 2-3 Applications of Linear Equations Solving Applied Problems. Note: The following six steps are useful in developing a technique for solving applied problems. • Step 1: Read the problem carefully until you understand what is given and what is to be found. • Step 2: Assign a variable to represent the unknown value, using diagrams or tables as needed. • Step 3: Write an equation using the variable expressions. • Step 4: Solve the equation. (Isolate the variable on the left side of the equals sign) • Step 5: State the answer with appropriate units. (Does it seem reasonable?) • Step 6: Check the answer.
  • 23. 23 2-3 Applications of Linear Equations Solving Applied Problems. At the end of the 1999 baseball season, Sammy Sosa and Mark McGwire had a lifetime total of 858 homeruns. McGwire had 186 more than Sosa. How many runs did each player have? • Step 1: Total runs = 858 Sosa has 186 less than McGwire • Step 2: Let x = Sosa’s runs, then x + 186 = McGwire’s runs • Step 3: x + (x + 186) = 858 • Step 4: 2x + 186 = 858 2x = 672 x = 336 x + 186 = 522 • Step 5: Sosa had 336 homeruns. McGwire had 522 homeruns. • Step 6: 336 + 522 = 858 858 = 858 Checked:
  • 24. 24 2-3 Applications of Linear Equations Solving Applied Problems. A woman has $34,000 to invest. She invests some at 17% and the balance at 20%. Her total annual interest income is $6425. Find the amount invested at each rate. • Step 1: Total investment = $34,000 Total interest earned is $6245 • Step 2: Let x = amount at 17%, then $34,000 - x = amount at 20% • Step 3: .17x + .20(34,000 - x) = 6245 • Step 4: .17x + 6800 - .20x = 6245 -.03x = -555 x = 18,500 34,000 – 18,500 = 15,500 • Step 5: $18,500 invested at 17% $15,500 invested at 20% • Step 6: .17(18,500) + .20(15,5000 = 6245 3145 + 3100 = 6245 6245 = 6245 Checked:
  • 25. 25 2-3 Applications of Linear Equations Solving Applied Problems. How many pounds of candy worth $8 per lb should be mixed with 100 lb of candy worth $4 per lb to get a mixture that can be sold for $7 per lb? • Step 1: Total mixture should sell for $7/lb. Given 100 lbs at $4/lb and an unknown amount at $8/lb. • Step 2: Let x = amount at $8 then x + 100 should sell at $7/lb • Step 3: 8x + 4(100) = 7(x + 100) • Step 4: 8x + 400 = 7x + 700 x = 300 • Step 5: 300 lb at $8/lb • Step 6: 8(300) + 4(100) = 7(300 + 100) 2400 + 400 = 7(400) 2800 = 2800 Checked:
  • 26. 26 2-3 Applications of Linear Equations Solving Applied Problems. How much water must be added to 20 L of 50% antifreeze solution to reduce it to a 40% antifreeze solution? • Step 1: Total mixture should be 40% antifreeze. Given 20 L at 50% produces 10 L of water and 10 L of antifreeze. Add an unknown amount of water. • Step 2: Let x = amount of water added, then x + 10 will be the water in the final solution and the amount of antifreeze is 10 L. • Step 3: • Step 4: amount percent percent  100%   100%  base a b 10 L of antifreeze  100%  40 10 L of antifreeze + (x+10) of water 1000  40(10  (  10)) 1000  400  40  400 40  200 5 x x x x  10 L of antifreeze • Step 5: 5 L of water • Step 6: Check: 100% 40% 10 L of antifreeze + (5+10) of water 10 100% 40% 25 40% 40%     
  • 27. 27 2-5 Linear Inequalities in One Variable Interval Notation is used to write solution sets of inequalities. Note: A parenthesis is used to indicate an endpoint in not included. A square bracket indicates the endpoint is included. Interval Notation Type of Interval Set Interval Notation Graph {x a  x } (a, ) {x  a  x  b} (a, b) {x  x  b} (-, b) {x  x is a real number} (-, ) Open Interval ( a ) b ( a ) b
  • 28. 28 2-5 Linear Inequalities in One Variable Interval Notation is used to write solution sets of inequalities. Note: A parenthesis is used to indicate an endpoint in not included. A square bracket indicates the endpoint is included. Interval Notation Type of Interval Set Interval Notation Graph {x a  x} [a, ) {x  a  x  b} (a, b] {x  a  x  b} [a, b) {x  x  b} (-, b] Half-open Interval [ a ] b ] b ( a ) b [ a
  • 29. 29 2-5 Linear Inequalities in One Variable Interval Notation is used to write solution sets of inequalities. Note: A parenthesis is used to indicate an endpoint in not included. A square bracket indicates the endpoint is included. Interval Notation Type of Interval Set Interval Notation Graph Closed Interval {x a  x  b} [a, b] ] b [ a
  • 30. 30 2-5 Linear Inequalities in One Variable A linear inequality in on variable can be written in the form Ax + B = C, where A, B, and C are real numbers with A  0. Note: The next examples include definitions and rules for < , >, , and  . • Examples of linear inequalities: x + 5 < 2 x – 3 > 5 2k +4  10
  • 31. 31 2-5 Linear Inequalities in One Variable Solving linear inequalities using the Addition Property: For all real numbers A, B, and C, the inequalities A < B and A + C < B + Ca are equivalent. Note: As with equations, the addition property can be used to add negative values or to subtract the same number from each side . • Example 1: Solve k – 5 > 1 k – 5 +5 > 1 + 5 k > 6 Solution set: (6,) • Example 2: Solve 5x + 3  4x – 1 and graph the solution set. 5x – 4x  -1 –3 x  -4 Solution set: [-4,) [ -4
  • 32. 32 2-5 Linear Inequalities in One Variable Solving linear inequalities using the Multiplication Property: For all real numbers A, B, and C, with C  0 , 1) if C > 0, then the inequalities A < B and AC < BC are equivalent. 2) if C < 0, then the inequalities A < B and AC > BC are equivalent. Note: Multiplying or Dividing by a negative number requires the inequality sign be reversed. • Example 1: Solve -2x < 10 x > -5 Solution set: (-5,) • Example 2: Solve 2x < -10 x < -5 Solution set: (-,-5) Note: The first example requires a symbol change because both sides are multiplied by (-1/2). The second example does not because both sides are multiplied by (1/2)
  • 33. 33 2-5 Linear Inequalities in One Variable Solving linear inequalities using the Multiplication Property: • Example 3: Solve –9m < -81 and graph the solution set m > 9 Solution set: (9, ) ( 9
  • 34. 34 2-5 Linear Inequalities in One Variable Solving a Linear Inequality: Step 1: Simplify each side separately. If necessary, use the distributive property to clear parenthesis and combine like terms. Step 2: Use the addition property to get all terms containing the specified variable on the left side of the inequality sign and all other terms on the right side. Step 3: Isolate the variable. (Use the multiplication (division) property to get an inequality where the coefficient of the variable is 1.) • Example 4: Solve 6(x-1) + 3x  -x –3(x + 2) and graph the solution set Step 1: 6x-6 + 3x  -x –3x – 6 9x - 6  –4x – 6 Step 2: 13x  0 Step 3: x  0 Solution set: [0, ) [ 0
  • 35. 35 2-5 Linear Inequalities in One Variable Solving a Linear Inequality: • Example 5: Solve and graph the solution set Step 1: Step 2: Step 3: 1 3 ( 3) 2 ( 8) 4 4 Solution set: [ , ) m   m m m m m [ -13/2 1 3 3 2 6 4 4 4 1 11 3 24 4 4 4 4 1 3 24 11 m m 4 4 4 4 2 13 4 4 13 2 m m               13 2 
  • 36. 36 2-5 Linear Inequalities in One Variable Solving applied problems using linear inequalities: • Example 6: Solve 5 < 3x – 4 < 9 and graph the solution set 5 + 4 < 3x < 9 + 4 9 < 3x < 13 3 < x < (13/3) Solution set: ( 3, ) 13 2 ) ( 3 13 2
  • 37. 37 2-5 Linear Inequalities in One Variable Solving applied problems using linear inequalities: Note: Expressions for inequalities sometimes appear as indicated in the table: Word Expression Interpretation • Example 7: Teresa has been saving dimes and nickels. She has three times as many nickels as dimes and she has at least 48 coins. What is the smallest number of nickels she might have? Let: x equal the number of dimes Then: 3x is the number of nickels and: 3x + x  48 4x  48 x  12  36 nickels a is at least b a is no less than b a is at most b a is no more than b a  b a  b a  b a  b
  • 38. 38 2-5 Linear Inequalities in One Variable Solving applied problems using linear inequalities: • Example 8: Michael has scores of 92, 90, and 84 on his first three tests. What score must he get on the 4th test in order to maintain an average of at least 90? Let: x equal the 4th score 92 90 84 : 90 4 266 90 4 266 360 360 266 94 x Then x x x x           