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SSC Selection Post 2022 PYQ — Question 71

SSC Selection Post - Matriculation Level - 3 Feb 2022 - Shift 3 • Quantitative Aptitude • Q71

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If x+1x=5x+ {{1} \over x}=5 , then find the value of x2+1x2.x^2+ {{1} \over x^2}.

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Correct answer: D

Explanation

The correct answer is Option 4 i.e. 23.

(x+1x)2=x2+1x2+2\left(x + \frac{1}{x} \right)^2 = x^2 + \frac{1}{x^2} + 2

(x+1x)2=52=25\left(x + \frac{1}{x} \right)^2 = 5^2 = 25

x2+1x2=25−2=23x^2 + \frac{1}{x^2} = 25 - 2 = 23