Question

How do you solve 4x-y=-9 and 2x+y=-3?

Answer 1

`(x,y)=(-2,1)`

Explanation:

[1]`color(white)("XXX")4x-y=-9`
[2]`color(white)("XXX")underline(2x+y=-3)`
[3]`color(white)("XXX")6xcolor(white)("XxX")=-12color(white)("XXX")` after adding [1] and [2]

[4]`color(white)("XXX")x=-2color(white)("XXXXXXX")`after dividing both sides of [3] by `6`

[5]`color(white)("XXX")-8-y=-9color(white)("XXXX")`after substituting `(-2)` for `x` in [1]

[6]`color(white)("XXX")y=1color(white)("XXXXXXX")`after adding `8` to both sides of [5] then dividing by `(-1)`