How do you solve the following system?: $-8x+3y=12 , 8x-9y= 12$

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Answer 1 · 2018-03-14T14:00:03

$x=-3, y=-4$

Given: $8x-9y=12$ . Solve for x.
$8x-9y+9y=12+9y$
$8x=12+9y$
$(8x)/8=(12+9y)/8$

$x=(12+9y)/8$

Substitute this into the other equation:

$-8x+3y=12$

$-8((12+9y)/8)+3y=12$

$-1(12+9y)+3y=12$

$-12-9y+3y=12$

$-12-6y=12$

$-12-6y+12=12+12$

$-6y=24$

$(-6y)/-6=24/-6$

$y=-4$

Substitute into original equation:

$8x-(9*-4)=12$

$8x+36=12$

$8x+36-36=12-36$

$8x =-24$

$(8x)/8=-24/8$

$x=-3$

To check, substitute both answers into both the formulas:

$-8*-3+3*-4=24-12=12$ True

$8*-3-9*-4=-24+36=12$ True

How do you solve the following system?: -8x+3y=12 , 8x-9y= 12 -8x+3y=12 , 8x-9y= 12