a, \(\left(2x+\dfrac{1}{2}\right)^3=8x^3+\dfrac{3.4x^2.1}{2}+\dfrac{3.2x.1}{4}+\dfrac{1}{8}=8x^3+6x^2+\dfrac{3}{2}x+\dfrac{1}{8}\)
b, \(\left(3x-y\right)^3=27x^3-3.9x^2.y+3.3x.y^2-y^3=27x^3-27x^2y+9xy^2-y^3\)
c, \(\left(\dfrac{1}{3}x+\dfrac{1}{2}y\right)^3=\dfrac{1}{27}x^3+3.\dfrac{1}{9}x^2.\dfrac{1}{2}y+3.\dfrac{1}{3}x.\dfrac{1}{4}y^2+\dfrac{1}{8}y^3=\dfrac{1}{27}x^3+\dfrac{1}{6}x^2y+\dfrac{1}{4}xy^2+\dfrac{1}{8}y^3\)
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