\(\left(3x^3y-\dfrac{1}{2}x^2+\dfrac{1}{5}xy\right).6xy^3\)
\(=18x^4y^4-3x^3y^3+\dfrac{6}{5}x^2y^4\)
\(\left(3x^3y-\dfrac{1}{2}x^2+\dfrac{1}{5}xy\right).6xy^3\)
\(=3x^3y.6xy^3-\dfrac{1}{2}x^2.6xy^3+\dfrac{1}{5}xy.6xy^3\)
\(=18x^4y^4-3x^3y^3+\dfrac{6}{5}x^2y^4\)