Answer:
A
Explanation:
x^4-64=0
factor
(x^2+8)(x^2-8)=0
zero property
x^2+8=0, x^2-8=0
x^2=0-8-8,
x^2=-8,
x^2=0+8=8,
x^2=8,
----------------
sqrt(8) & sqrt(-8),
gives you 2*sqrt(2) and -2*sqrt(2),
also, the square root of a negative number contains the imaginary number, i. Because sqrt(-1)=i, don't forget this formula.
So sqrt(-8)=2i*sqrt(2) and -2i*sqrt(2).