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SSC CGL 2024 PYQ — Question 60

SSC CGL - 25 Sep 2024 - Shift 3 • Quantitative Aptitude • Q60

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If x2+1=xx^2+1=x, then the value of (x15+x9+1)(x^{15}+x^9+1) is:

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Correct answer: C

Explanation

The correct answer is option 3 i.e. -1.

x2 + 1 = x

⇒ x2 - x + 1 = 0

So, x3 = - 1   [If x2 - x + 1 = 0 then x3 = - 1]

Now, x15 + x9 + 1

= (x3)5 + (x3)3 + 1

= (- 1)5 + (- 1)3 + 1

= - 1 - 1 + 1 = - 1