EASY! Factorise x^4-1?

Indeed this is easy...
to factorize, means simply place in brackets (expand is to take out of the brackets)
x^4-1
= (x^2-1)(x^2+1) is the correct answer

To check this, (help you understand why) lets expand the brackets (Using the F.O.I.L rule (Multiply the First in each bracket together, then the Outer of each bracket, than the Inner, and finally the Last))
(x^2-1)(x^2+1)
= x^4 + x^2 - x^2 -1
= x^4-1

x^4-1
=(x^2-1)(x^2+1)
=(x-1)(x+1)(x^2+1)

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

x^4 - 1
= x^4 - 1^4
= (x^2)^2 - (1^2)^2
= (x^2 + 1)(x^2 - 1)
= (x^2 + 1)(x^2 - 1^2)
= (x^2 + 1)(x + 1)(x - 1)

x^4-1
=(x^2+1)(x^2-1)
=(x^2+1)(x+1)(x-1) answer//