Given:
Equation 1: 2x + 3y = 7
Equation 2: 2ax + (a + b)y = 28
Both the equations are in the form of :
a1x + b1y = c1 & a2x + b2y = c2 where
a1 & a2 are the coefficients of x
b1 & b2 are the coefficients of y
c1 & c2 are the constants
For the system of linear equations to have infinitely many solutions we must have
According to the problem:
a1 = 2
a2 = 2a
b1 = 3
b2 = (a + b)
c1 = 7
c2 = 28
Putting the above values in equation (i) we get:
To obtain the value of a & b we need to solve the above equality. First we solve the extreme left and extreme right of the equality to obtain the value of a.
⇒
⇒ 2a x 7 = 2 x 28
⇒ 14a = 56
⇒ a = 4
After obtaining the value of a we again solve the extreme left and middle portion of the equality (ii)
⇒ 2 x (4 + b) = 3 x 2 x 4
⇒ b + 4 = 12
⇒ b = 8
The value of a & b for which the system of equations has infinitely many solution is a = 4 & b = 8