Question

x-1/9x=1 find 27x^3-1/27x^3

Answer 1

Hope u like my process
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Formula to be used
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=> a³ - b³ =(a-b)³ +3ab(a-b)
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$= > x - \frac{1}{9x} = 1 \\ \\ \bf \: multiplying \: \: both \: \: sides \: \: by \: \: 3 \\ \\ = > 3x - \frac{1}{3x} = 3 \\ \\ \: \: \: \: \: \: \: \: \: \bf \underline{now} \\ \\ = > 27 {x}^{3} - \frac{1}{27 {x}^{3} } \\ \\ = {(3x)}^{3} - {( \frac{1}{3x}) }^{3} \\ \\ = {(3x - \frac{1}{3x}) }^{3} + 3(3x)( \frac{1}{3x} )(3x - \frac{1}{3x} ) \\ \\ = {(3)}^{3} - 3 \times 1 \times (3) \\ \\ = 27 - 9 = \bf \underline{18}$
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