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SSC Selection Post 2022 PYQ — Question 56

SSC Selection Post - Matriculation Level - 3 Feb 2022 - Shift 2 • Quantitative Aptitude • Q56

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If x+1x=4x+{{1} \over x}=4 ,then find the value of x3+1x3x^3+{{1} \over x^3}

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Correct answer: B

Explanation

The correct answer is option 2 i.e. 52.

Given, x+1x=4x+{{1} \over x}=4

Cubing both sides,

⇒ (x+1x)3=(4)3(x+{{1} \over x})^3=(4)^3

⇒ x3+1x3+3(x)(1x)(x+1x)x^3+{{1} \over x^3} + 3(x)(\frac{1}{x})(x + \frac{1}{x}) = 64

⇒ x3+1x3+12x^3+{{1} \over x^3} + 12 = 64

⇒ x3+1x3x^3+{{1} \over x^3} = 52