Question

How do you factor `a^3 - ab^2 - 2a^2 + 2b^2`?

Answer 1

Collect `a^2` between the first and third term and `-b^2` between the second and forth:
`a^2(a-2)-b^2(a-2)=` now collect `(a-2)`:
`=(a-2)(a^2-b^2)=(a-2)(a-b)(a+b)`