原式=5x√(xy)÷3√(y/x)×1/3√(x/y)
=5x÷3×1/3×√(xy÷y/x×x/y)
=(5/9)x×√(xy×x/y×x/y)
=(5/9)x×√[xy×(x/y)²]
=(5/9)x×x/y×√(xy)
=(5x²√xy)/(9y)