Question

Solve for y in `2x + y = 1` and `x - 2y =-7`?

Answer 1

If `2x+y=1`
then
`4x+2y = 2`

We can add the second equation to this to eliminate the `y` term

`((,4x,+,2y,=,2),(+,x,-,2y,=,-7),(,5x,,,=,-5))`

`rarr x=-1`

Substituting `x=-1` back into the original first equation we get
`2(-1) + y = 1`
which simplifies as
`y=3`