h: \(\left(2x^2+y\right)^3\)
\(=\left(2x^2\right)^3+3\cdot\left(2x^2\right)^2\cdot y+3\cdot2x^2\cdot y^2+y^3\)
\(=8x^6+12x^4y+6x^2y^2+y^3\)
i: \(\left(\dfrac{1}{2}x^2+y\right)^3\)
\(=\left(\dfrac{1}{2}x^2\right)^3+3\cdot\left(\dfrac{1}{2}x^2\right)^2\cdot y+3\cdot\dfrac{1}{2}x^2\cdot y^2+y^3\)
\(=\dfrac{1}{8}x^6+\dfrac{3}{4}x^4y+\dfrac{3}{2}x^2y^2+y^3\)
k: \(\left(3x-y\right)^3=\left(3x\right)^3-3\cdot\left(3x\right)^2\cdot y+3\cdot3x\cdot y^2-y^3\)
\(=27x^3-27x^2y+9xy^2-y^3\)
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