How do you solve the following system?: 13x -17y =21, -7x -4y = -7

1 Answer
Nov 20, 2015

(307/171,-238/171)

Explanation:

Multiply the first equation by 7, and the other by 13.

7*(13x-17y) =7*21
91x-119y=147

13*(-7x-4y)=13*-7
-91x-52y=91

Then add these two equations.

91x-119y=147
-91x-52y=91

91x-119y-91x-52y=147+91
-171y=238
y=-238/171

Now write -238/171 instead of y in one of the equations.

-7x+4*238/171=-7
x=307/171