How do you solve the system of equations 4x - 5y = 25 and - 7x + 3y = 8?

1 Answer
Feb 13, 2018

x=-5 and y =-9

Explanation:

4x - 5y = 25------------(1)

- 7x + 3y = 8 -----------(2)

First eliminate any one variable (say y),

(1) xx 3 + (2) xx 5 =>

=>12x - 15y -35x + 15y =75 + 40

=> 12x-35x -cancel(15y)+cancel(15y) = 115

=> -23 x =115

=> x = -5

Substitute this value of x in any one equation.

(1) => 4xx(-5) -5y =25

=> -20 -5y =25

=> y = (25+20)/-5

y = -9

So, x=-5 and y =-9

Verify by substituting both values in equation (2):

Left hand side of equation = -7x+3y

=> -7xx(-5) +3xx(-9) = 35 - 27 = 8 = Right hand side.

Hence verified.