Question

How do you solve `-2x+7y=9` and `3x+2y=-1` using substitution?

Answer 1

`y=1 , x=-1`

Explanation:

`-2x+7y=9`---------(1)
`3x+2y=-1`---------(2)
`-6x+21y=27`---`(1) xx 3` ----(3)
`6x+4y=-2`---`(2) xx 2` -----(4)
`25y=25`--------------(3)+(4)
multiply both sides by `1/25`

`1/cancel25^1 xx cancel25^1/1y=cancel25^1/1 xx 1/cancel25^1`

`y=1`

substitute y=1 in (2)

`-2x+7(1)=9`

`-2x+7=9`

`-2x=9-7`

`-2x=2`

`2x=-2`

`x=-2/2`

`x=-1`
substitute# x=-1 and y=1 in (1)

`-2(-1)+7(1)=9`

`2+7=9`