\(7xy^2.\left(\dfrac{1}{7}x^2y^3+3x^2+1\right)\)
\(=7xy^2.\dfrac{1}{7}x^2y^3+7xy^2.3x^2+7xy^2.1\)
\(=x^3y^5+21x^3y^2+7xy^2\)
Ta có:
\(7xy^2\cdot\left(\dfrac{1}{7}x^2y^3+3x^2+1\right)\)
\(=7xy^2\cdot\dfrac{1}{7}x^2y^3+7xy^2\cdot3x^2+7xy^2\cdot1\)
\(=x^3y^5+21x^3y^2+7xy^2\)