Ta có: \(\left(3xy^2+\dfrac{1}{3}x^2y\right)^3\)
\(=\left(3xy^2\right)^3+3\cdot\left(3xy^2\right)^2\cdot\dfrac{1}{3}x^2y+3\cdot3xy^2\cdot\left(\dfrac{1}{3}x^2y\right)^2+\left(\dfrac{1}{3}x^2y\right)^3\)
\(=27x^3y^6+9x^4y^5+x^5y^4+\dfrac{1}{27}x^6y^3\)