3. In this lecture we shall
Inequalities
Absolute values
Graph and coordinate
4. Inequality
In mathematics, an inequality is a relation that holds between
two values when they are different.
This comparison is expressed by using the inequality symbols
6. The symbol means ; either ora b a b a b
These four expression are equivalent
a is greater than or equal to ba b
a is less than or equal to ba b
7. The symbols < and > are called strict inequality, and the symbols
and are called weak inequalities
Rules for working with inequalities symbols
Addition
Subtraction
Multiplication
Division
8. Summary of operation on inequalities
You can add or subtract a number on both side of an inequality.
You can multiply or divide an inequality by a positive number.
You can multiply or divide an inequality by a negative number, but you
must change the direction of inequality.
9. Relation between interval and inequality
Interval notation inequality notation
,
,
,
,
,
,
,
,
,
a b
a b
a b
a b
b
b
a
a
Graph
10. How to graph the solutions
Graph any number greater than. . .
open circle, line to the right
Graph any number less than. . .
open circle, line to the left
Graph any number greater than or equal to. . .
closed circle, line to the right
Graph any number less than or equal to. . .
closed circle, line to the left
12. Examples
As the altitude of a shuttle increases, an astronaut’s weight decreases
until a state of weightless is achieved. The weight of a 125-lb astronaut at
an altitude of x kilometer above see level is given by
At what altitude is the astronaut’s weight less then 5lb?
??
2
6400
125
6400
w
x
20. If a and b are real number then
Theorem
a a
ab a b
aa
b b
21. Graph and coordinate
A rectangular coordinate system is a pair of perpendicular coordinate lines,
called coordinate axes, which are placed so that they intersect at their origins.
22. The labeling of axis's with letters x and y is a common convention, but any
letters may be used. If the letter x and y are used to label the coordinate
axes, then the resulting plane is called xy-plane. In applications it is
common to use letters other than x and y is shown In the following figures,
as uv-plane and ts-plane.
23.
24. For example if we take (a,b)=(4,3), then on coordinate plane
To plot a point P(a,b) means to locate the point with coordinates (a,b) in a
coordinate plane. For example, different points are plotted.
26. Solve the inequality and express the solution in terms of
intervals whenever possible.
4 1
2 0
3
x
6 5 3x
1
2
2 3
x
x
Sketch the graph of the equation
2
2
2 1
4
y x
y x
Exercise