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Mathematics

By using standard formulae, expand the following:

(3x+1x)3\Big(3x + \dfrac{1}{x}\Big)^3

Expansions

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Answer

(3x+1x)3=(3x)3+(1x)3+3(3x)(1x)(3x+1x)=27x3+1x3+27x+9x\Big(3x + \dfrac{1}{x}\Big)^3 = (3x)^3 + \Big(\dfrac{1}{x}\Big)^3 + 3(3x)\Big(\dfrac{1}{x}\Big)\Big(3x + \dfrac{1}{x}\Big) \\[1em] = 27x^3 + \dfrac{1}{x^3} + 27x + \dfrac{9}{x}

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