\(=-4xy^2\cdot\dfrac{1}{2}x^2y^3+4xy^2\cdot\dfrac{3}{8}x^3y-4xy^2\cdot5x\)
\(=-2x^3y^5+\dfrac{3}{2}x^4y^3-20x^2y^2\)
\(-4xy^2\left(\dfrac{1}{2}x^2y^3-\dfrac{3}{8}x^3y+5x\right)=-2x^3y^5+\dfrac{3}{2}x^4y^3-20x^2y^2\)
=-2x\(^3\)y\(^5\) + \(\dfrac{3}{2}\)x\(^4\)y\(^3\)-20x\(^2\)y\(^2\)