Question

How do you use the substitution method to solve 3x-15y=-12 and 3x+24y=-12?

Answer 1

Derive an expression for `3x` from the first equation, then substitute that in the second equation and solve to find `y = 0` and `x = -4`

Explanation:

First add `15y` to both sides of the first equation to get:

[1] `3x=15y-12`

Then substitute `15y-12` for `3x` in the second equation to get:

`(15y-12)+24y=-12`

Add `12` to both sides and combine the remaining terms to get:

`39y = 0`

Divide both sides by `39` to get `y = 0`

Then substitute `y=0` in [1] to get:

`3x = -12`

Divide both sides by `3` to get `x = -4`