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SSC CHSL 2023 PYQ — Question 70

SSC CHSL - 09 Aug 2023 - Shift 1 • Quantitative Aptitude • Q70

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 If x2 - 4x - 1= 0, then find the value of x2 +1x2\frac{1}{x^2}-5

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Correct answer: C

Explanation

The correct answer is option 3 i.e. 13.

x2 - 4x - 1 = 0

⇒ x2 - 1 = 4x

⇒ x - 1/x = 4

⇒ (x - 1/x)2 = 42

⇒ x2 - 2 + 1/x2 = 16

⇒ x2 + 1/x2 = 18

⇒ x2 + 1/x2 - 5 = 18 - 5 = 13

Therefore, the value of x2 + 1/x2 - 5 is 13.