Question

How do you solve `xy=144` and `x-y=18`?

Answer 1

Use substitution and factoring

Explanation:

`xy=144`
`x-y = 18`
`:.x = 18+y`

Substituting this into the first equation gives
`(18+y)y=144`
`18y +y^2 - 144=0`
`(y^2+18y-144)=0`
`(y+24)(y-6)=0`

`y=-24` or `y=6`
`x=-6` or `x=24`