Question

5th root(8x^3/y^4)*5th root(4x^4/y^2)

Answer 1

Both are to the 5th square root, so you can multiply what is inside:
that is $\sqrt[5]{ \frac{2^{5} x^{7} }{ y^{6} } }$
=$\frac{2x}{y} \sqrt[5]{\frac{ x^{2} }{y} }$