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Mathematics

By using standard formulae, expand the following:

(2x+3x1)2\Big(2x + \dfrac{3}{x} - 1\Big)^2

Expansions

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Answer

(2x+3x1)2=[(2x)+(3x)+(1)]2=(2x)2+(3x)2+(1)2+2[(2x)(3x)+(3x)(1)+(1)(2x)]=4x2+9x2+1+2[63x2x]=4x2+9x2+1+126x4x=4x2+9x2+136x4x\Big(2x + \dfrac{3}{x} - 1\Big)^2 = \Big[\Big(2x\Big) + \Big(\dfrac{3}{x}\Big) + \Big(-1\Big)\Big]^2 \\[1em] = (2x)^2 + \Big(\dfrac{3}{x}\Big)^2 + (-1)^2 + 2 \Big[\Big(2x\Big)\Big(\dfrac{3}{x}\Big) + \Big(\dfrac{3}{x}\Big)\Big(-1\Big)+\Big(-1\Big)\Big(2x\Big) \Big] \\[1em] = 4x^2 + \dfrac{9}{x^2} + 1 + 2\Big[6 - \dfrac{3}{x} - 2x \Big] \\[1em] = 4x^2 + \dfrac{9}{x^2} + 1 + 12 - \dfrac{6}{x} - 4x \\[1em] = 4x^2 + \dfrac{9}{x^2} + 13 - \dfrac{6}{x} - 4x \\[1em]

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