solve by factoring a^2-4ab-8b^2?

Answer 1

No factors over the integers. But, you do have

(a-2b)^2 - 12b^2
as a difference of two squares, that'd be

(a-2b + √12 b)(a-2b - √12 b)
or
(a-2(1-√3)b)(a-2(1+√3)b)