Question

Factor x4 – 81. Question 20 options: A) (x2 + 3)(x2 – 3) B) (x2 – 9)(x + 3)(x – 3) C) (x2 + 9)(x + 3)(x – 3) D) (x + 3)2(x – 3)2

Answer 1

C is correct

Explanation:

A square minus a square can always be factored into the square root of the 1st term plus and minus the square root of the 2nd term. So

x**4 - 81 = (x**2 + 9)(x**2 -9) = (x**2 + 9) (x + 3)(x - 3)