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

Question

3153 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-06-03T18:31:20

Given:

$3a+b = -1$

$-3a+b=5$

First add both equations together to get:

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

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

Then subtract both equations to get:

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

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

How do you solve the system using elimination 3a + b = -13a + b = -1 and -3a + b = 5-3a + b = 5?