(8a^8)^.5
Did you mean simplify?
A nice way to do this: factor the radicand (do you know what that is?) using the largest factors you can find the square root of. then break the problem into two sqaure roots. In the first, throw everything that simplifies, in the last, everything that doesn't
$\displaystyle \sqrt{8a^8} = \sqrt{4 \cdot 2 \cdot a^8}$
$\displaystyle = \sqrt{4a^8} \cdot \sqrt 2$
$\displaystyle = 2a^4 \sqrt 2$