a) \(\left(\dfrac{1}{2}x^2+\dfrac{1}{3}y\right)^3=\left(\dfrac{1}{2}x^2\right)^3+\left(3.\dfrac{1}{4}x^4.\dfrac{1}{3}y\right)+\left(3.\dfrac{1}{2}x^2.\dfrac{1}{9}y^2\right)+\left(\dfrac{1}{3}y\right)^3\)
\(=\dfrac{1}{8}x^6+\dfrac{1}{4}x^4y+\dfrac{1}{6}x^2y^2+\dfrac{1}{27}y^3\)
b) \(\left(3x^2-2y\right)^3=\left(3x^2\right)^3-\left(3.9x^4.2y\right)+\left(3.3x^2.4y^2\right)-\left(2y\right)^3\)
\(=27x^6-54x^4y+36x^2y^2-8y^3\)
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