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SSC CGL 2024 PYQ — Question 68

SSC CGL - 25 Sep 2024 - Shift 1 • Quantitative Aptitude • Q68

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If a3+1a3=2(a>0)a^3 + \frac{1}{a^3} = 2 (a > 0) , then the value of a+1aa + \frac{1}{a} is:

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Correct answer: C

Explanation

The correct answer is option 3 i.e. 2.

If x + (1/x) = a then x3 + 1/x3 = a3 - 3a

a3 + 1/a3 = 2

Let, a + 1/a = x

Now, x3 - 3x = 2

⇒ x3 - 3x - 2 = 0

If x = 2 then 23 - 3(2) - 2 = 8 - 6 - 2 = 0

So, x = 2

Therefore, the required value is 2.