Mathematics Pre=Cal?

Question

Can someone help me to figure out this problem, or @ least some steps that may help? thank you in advance

Solve x^4-1=0 in three ways. Divide out rational roots, factor in two quadratic factors, and find the four fourth roots , using De Moivre's theorem?

Answer 1

1. x^4 - 1 = 0
x^4 = 1
x^2 = +-sqr(1) = +-1, for rational roots, only +1 will work
x=sqr(1)= +-1

2. x4-1 = (x^2-1)(x^2+1) = (x+1)(x-1)(x^2+1) =0

3. The answer here should be obvious