Question

How do you FOIL `(2x - 5y) ( x + y)`?

Answer 1

Given `(2x-5y)(x+y)` pick out pairs of terms to multiply in the order given by FOIL:

First: `2x xx x = 2x^2`
Outside: `2x xx y = 2xy`
Inside: `-5y xx x = -5yx = -5xy`
Last: `-5y xx y = -5y^2`

Then add these all together to get:

`2x^2+2xy-5xy-5y^2 = 2x^2-3xy-5y^2`