(2x2y4)3/2=23/2x2×3/2y4×3/2=√8(x3y6). What does 23/2 actually mean? Well, we could write it as (23)½, because 3×½=3/2. But 23=2×2×2=8. And raising anything to the power of ½ is the same as finding the square root. So 8½=√8.
Another way to work out 23/2 is to write it as 21½=212½=2√2.
√8=√(22×2)=(√22)(√2)=2√2, so the answer is (2x2y4)3/2=2√2x3y6.