what is the square root of x4

Answer 1

If you mean x⁴, that is
(x⁴)^1/2 = x²

Answer 2

Do you mean of x^4 ?
if so
(x^4)^1/2 = x^(4 *.5) = x^2

prove it to yourself:

sqrt (x*x*x*x) = x*x

Answer 3

thanks