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SSC CHSL 2023 PYQ — Question 70

SSC CHSL - 10 Aug 2023 - Shift 3 • Quantitative Aptitude • Q70

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If x2−9.76x+1=0x^2-\sqrt{9.76}x+1=0 and x > 1, the value of (x3−1x3)(x^3-\frac{1}{x^3}) is:

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Correct answer: C

Explanation

The correct answer is option 3 i.e. 21.024.

x2 - √(9.76)x + 1 = 0

⇒ x - √(9.76) + 1/x = 0

⇒ x + 1/x = √(9.76)

⇒ x - 1/x = √{(√9.76)2 - 4} = √(9.76 - 4) = √5.76 = 2.4

⇒ x3 - (1/x3) = (2.4)3 + 3 × 2.4 = 13.824 + 7.2 = 21.024

Therefore, the value of the expression is 21.024.