Question

How do you factor `r^2-25tw+5wr-5tr`?

Answer 1

It helps to swap the terms around a little first so that the coefficients of the 1st and 2nd terms are in the same ratio as the 3rd and 4th terms thus:

`r^2-25tw+5wr-5tr`

`= r^2+5wr-5tr-25tw`

`= (r^2+5wr)-(5tr+25tw)`

`= r(r+5w)-5t(r+5w)`

`= (r-5t)(r+5w)`