# How do you solve the system 8x + 3y= -9 and -8x + y = 29 by elimination?

May 23, 2015

Given
$\text{[1] } 8 x + 3 y = - 9$
$\text{[2] } - 8 x + y = 29$

Add $\text{[1] + [2]}$
$\text{[3] } \left(0\right) x + 4 y = 20$

Which implies
$\text{[4] } y = 5$

Substituting $\text{[4] }$ back into $\text{[1]}$
$\text{[5] } 8 x + 3 \left(5\right) = - 9$

Gives
$\text{[6] } x = - 3$

So the solution to the given pair of equations is
$\left(x , y\right) = \left(- 3 , 5\right)$