# How do solve the following linear system?:  x - 3y = 1, y = 4x + 4 ?

Dec 9, 2017

$x = - \frac{13}{11} , y = - \frac{8}{11}$

#### Explanation:

Since one of the equations is given to us as $y = \ldots$, we can substitute this into the first equation.

Subst. eqn 2 into eqn 1

$x - 3 \left(4 x + 4\right) = 1$
$x - 12 x - 12 = 1$
$- 11 x = 13$
$x = - \frac{13}{11}$

Subst. back into either of the other equations (I'll use the second, but both work).

$y = 4 \left(- \frac{13}{11}\right) + 4$
$y = - \frac{8}{11}$