Question

Y=-x-1 y=-2x+1 ?

Answer 1

`2=x`

Explanation:

Substitute the `-x-1` for `y` to get

`-x-1=-2x+1`

Add `x` to `-x` and `-2x` to get

`-1=-1x+1`

Subtract `1` from `1` and `-1` to get

`-2=-1x`

Divide both sides by `-1` to get

`2=x`

Answer 2

Linear algebra states that x=2, making y=-3

Explanation:

Linear algebra allows us to add and subtract whole equations from each other, like so:

`y=-2x+1`
`-`
`ul(y=-x-1)`
`0=-x+2`

Taking the solution from the bit of linear algebra we've done:
`0=-x+2 rArr color(red)(x=2)`

We can now plug our solution for `x` back into either of the equations and solve for `y`:

`y=-(2)-1 rArr y=-2-1 rArr color(red)(y=-3)`
`y=-2(2)+1 rArr y=-4+1 rArr color(red)(y=-3)`