# How do you solve the system using elimination 3a + b = -1 and -3a + b = 5?

Jun 3, 2015

Given:

$3 a + b = - 1$

$- 3 a + b = 5$

First add both equations together to get:

$4 = - 1 + 5 = \left(3 a + b\right) + \left(- 3 a + b\right) = 2 b$

Divide both ends by $2$ to get $b = 2$

Then subtract both equations to get:

$- 6 = - 1 - 5 = \left(3 a + b\right) - \left(- 3 a + b\right) = 6 a$

Divide both ends by $6$ to get $a = - 1$