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SSC Selection Post 2020 PYQ — Question 64

SSC Selection Post - Higher Secondary Level - 6 Nov 2020 - Shift 3 • Quantitative Aptitude • Q64

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If x4 - 3x2 - 1 = 0, then the value of (x6 - 3x2 + 3x2−1x6\frac{3}{x^2}-\frac{1}{x^6} + 1) is:

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Correct answer: C

Explanation

The correct answer is Option 3 i.e. 28.

x4 - 3x2 - 1 = 0

⇒ x2 - 1/x2 = 3

Now, x6 - 1/x6 = 33 + 3 × 3 = 36

⇒ x6 - 1/x6 - 3(x2 - 1/x2) + 1 = 36 - 3 × 3 + 1

⇒ x6 - 3x2 + 3/x2 - 1/x6 + 1 = 28