Question

How do I use substitution to find the solution of the system of equations `y=-2x-4` and `y+4=-2x`?

Answer 1

[1] `y = -2x - 4`
[2] `y + 4 = -2x`

If you isolate `y` in [2], the resulting equation is equal to [1]

`y + 4 = -2x`
`=> y = -2 - 4`

Since [1] is a linear equation, the domain is `RR`. This means that any value of `x` will yield the same valid value for both equations