Question

How do you factorise `5n - 2a n - 5m + 2a m`?

Answer 1

`=(n-m)(5-2a)`

Explanation:

There are 4 terms - group the terms in pairs, making sure there is a `+` sign between the pairs:

`(5n-5m)+(-2an+2am)" "larr` take out common factors:

`=5(n-m)color(magenta)(-2)a(n-m)" "larr` note the change of signs.

`=(n-m)(5-2a)`