In using radicals, square roots, and powers;

when trying to figure the square root of a number with a radical such as;

$\displaystyle (64x^8)^\frac{1}{2}$

Now in figuring out the $\displaystyle x^8$ from the square root I know that 64 is 8, but the $\displaystyle x^8$ is $\displaystyle x^4$ does this mean that in order to get 4 we subtract 4 from 8? Meaning that for figuring out the square root of 64 is basically division(multiplication) but on the radicals, is it subtraction(addition)!?

Hope I made sense...!!

Thanks