Hi all,

I feel pretty dumb posting this up, but here we go.

Factorise -

$\displaystyle 9a^2 - 4b^2 + 12a + 8b$

I don't know why, I just never seem to be able to find the right combination for these.

I know we're meant to type out a common factor, I can't spot it though

I.e. for ax + bx + ay + by = a (x + y) + b (x + y) -> (a + b)(x + y)

Anyone want to point out the obvious combination for me?