8sqrt(x^2y^6)
8sqrt(x•x•y•y•y•y•y•y)
Since there are 2 xs, we can pull them out of the radical.
8xsqrt(y•y•y•y•y•y)
Since there are 6 ys, we can pull them all out and there are 3 left now.
8xy^3
There is nothing left inside the radical so we can get rid of it!
Best wishes:)