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SSC CHSL 2019 PYQ — Question 67

SSC CHSL - 8th July 2019 - Shift 1 • Quantitative Aptitude • Q67

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If x = 2 + √3 then, the value of x3 + 1/x3 is:

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Correct answer: B

Explanation

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

If x + 1/x = a then, x3 + 1/x3 = a3 – 3a

Given:

⇒ x = 2 + √3

Then,

⇒ 1/x = 2 – √3

Now,

⇒ x + 1/x = 2 + √3 + 2 - √3

⇒  x + 1/x = 4

So, the value of x3 + 1/x3 

⇒ 43 – 3 × 4 = 64 – 12 = 52