1/5x的平方y乘以(-5xy)平方-(-2x)立方乘以xy立方

原式=1/5x²y×(-5xy)²-(-2x)³×xy³
=1/5x²y×(-5)²×x²×y²-(-2)³×x³×xy³
=1/5x²y×25x²y²-(-8)×x³×xy³
=(25×1/5)×(x²×x²)×(y×y²)+8×(x³×x)×y³
=5x^4y³+8x^4y³
=13x^4y³