A pair of linear equations in two variables can have different types of solutions: a unique solution (consistent), no solution (inconsistent), or infinitely many solutions (dependent). The document outlines methods for solving these equations algebraically, including substitution and elimination methods. Additionally, it provides examples of representing real-life situations with linear equations.

1. PAIR OF LINEAR EQUATIONS IN TWO VARIABLES

2. Equation which can be put in the form
ax + by + c = 0, where a, b and c are
real numbers, and a and b are not
both zero, is called a linear equation in
two variables x and y

3. The general form for a pair of linear
equations in two variables x and y is
a1x + b1y + c1 = 0 and a2 x + b2 y +
c2 = 0, where a1 , b1 , c1 , a2 , b2 , c2
are all real numbers.

5. the lines may intersect in a single point. In this case, the
pair of equations
has a unique solution (consistent pair of equations).
the lines may be parallel. In this case, the equations have
no solution
(inconsistent pair of equations).
the lines may be coincident. In this case, the equations have
infinitely many
solutions [dependent (consistent) pair of equations].

6. A pair of linear equations which has no solution, is
called an inconsistent pair of linear equations.
A pair of linear equations in two variables, which
has a solution, is called a consistent pair of linear
equations.
A pair of linear equations which are equivalent has
infinitely many distinct common solutions. Such a
pair is called a dependent pair of linear equations
in two variables. Dependent pair of linear
equations is always consistent.

7. ALGEBRAIC METHODS OF SOLVING A PAIR OF
LINEAR EQUATIONS
Substitution Method
Elimination Method
Cross - Multiplication Method

8. Solve the following pair of equations by
substitution method:
7x – 15y = 2 (1)
x + 2y = 3 (2)
X+2y=3, x= 3-2y
Sub x in equ 1
7(3-2y) – 15y = 2
21-14y-15y =2
21-29y=2
-29y= 2-21
-29y = -19
Y= 19/29
X= 3-2*19/29 = 49/29

9. Aftab tells his daughter, “seven years ago, I was seven times as old as you
were then. Also, three years from now, I shall be three times as old as you
will be.” Represent this situation algebraically.
x-7=7(y-7)
X-7=7y-49
X-7y=-49+7=-42
X-7y+42=0 (1)
X+3= 3(y+3)
X+3=3y+9
X-3y+3-9=0
X-3y-6=0 (2)
X-3y-6=0
X=3y+6 x= 3*12+6= 42
3y+6-7y+42=0
-4y+48=0
-4y=-48
y= 12

10. ELIMINATION METHOD