How to solve these using the factor/remainder theorem

1. Factorise the following.

(a) x^4 - a^4
(b) x^5 + a^5

(a) a^4 - b^4 = (a^2 + b^2)(a^2 - b^2) = (a2 + b^2)(a + b)(a - b)

(b) x^5 + a^5 = (x + a)(x^4 - x^3a + x^2a^2 - xa^3 + a^4)