Which choice is a factor of x^4-1 when factored completely? A. x^2-1 B. x C. x-1 D. 1

C. x-1 i think

This is a difference of perfect squares

Ok so remember that x^3 times x^3=x^6 so

remember that

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

so

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

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

possible factors are (x^2+1), (x^2-1), (x+1), (x-1)

facotred completely so have to chose from (x^2+1), (x+1), (x-1) since the (x^2-1) wasn't factored completely

the only match is C. x-1