Question

How do you factor 5x^4- 5x^2

Answer 1

The greatest common factor is 5x^2 so:

5x^2(x^2-1) (now notice that the parenthetical term is the difference of perfect squares)

The rule for factoring difference of squares is: a^2-b^2=(a-b)(a+b) so:

5x^2(x+1)(x-1)