# How do you solve x + y = -4 and y = -3x + 2 using substitution?

Jul 12, 2017

$\left(x , y\right) = \left(- 3 , - 7\right)$

#### Explanation:

$x + y = - 4 - - \left(1\right)$

$y = - 3 x + 2 - - \left(2\right)$

substitute for y from $\left(2\right) \text{ }$into $\text{ } \left(1\right)$

$x + - 3 x + 2 = - 4$

$- 2 x = - 4 - 2$

$\implies x = 3$

substitute into $\left(1\right)$ to find $y$
https://socratic.org/
$3 + y = - 4$

$\implies y = - 7$

$\therefore \left(x , y\right) = \left(3 , - 7\right)$

a quick mental check for $e q n \left(2\right)$ will see that the solution is consistent.