SarkariPYQ

SSC CGL 2021 PYQ — Question 73

SSC CGL - 24 Aug 2021 - Shift 3 • Quantitative Aptitude • Q73

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In the following passage, some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each blank.
John was an artist (1)______ profession. He was very (2)______ at his work and could
(3)______ any subject he could think of, but circumstances forced him to (4)______ in
(5)______ the work of renowned artists.

If x4 - 62x2 + 1 = 0, where x > 0, then the value of x3 + x-3 is :

Show answer & explanation

Correct answer: C

Explanation

The correct answer is option 3 i.e. 488

x4 - 62x2 + 1 = 0

Divide by x2

x2 - 62 + 1/x2 = 0

x2 + 1/x2 = 62

(x + 1/x)2 = x2 + 1/x2 + 2

(x + 1/x)2 = 62 + 2 = 64

x + 1/x = √64 = 8

(x + 1/x)3 = x3 + 1/x3 + 3(x + 1/x)

83 = x3 + 1/x3 + 3 × 8

x3 + 1/x3 = 512 - 24 = 488