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SSC Selection Post 2020 PYQ — Question 73

SSC Selection Post - Graduation Level 2020 - 9 Nov 2020 - Shift 3 • Quantitative Aptitude • Q73

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If x2 - 2√5x + 1 = 0, then which of the following is the value of x3 + 1x3\frac{1}{x^3}?

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Correct answer: D

Explanation

The correct answer is Option 4 i.e. 34534\sqrt5.

x2 - 2√5x + 1 = 0

⇒ x + 1/x = 2√5

⇒ x3 + 1/x3 = (2√5)3 - 3(2√5)

= 40√5 - 6√5

= 34√5