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SSC CHSL 2020 PYQ — Question 74

SSC CHSL - 20th October 2020 - Shift 2 • Quantitative Aptitude • Q74

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If x = 3 + 2√(2), then the value of x2 + (1/x2) is:

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Correct answer: D

Explanation

The correct answer is Option 4 i.e. 34.

Understanding/Application

x = 3 + 2√(2)

1/x = 1/(3 + 2√(2))

1/x = 1/(3 + 2√(2)) × (3 - 2√(2))/(3 - 2√(2))

1/x = (3 - 2√(2))/(9 - 8)

1/x = 3 - 2√(2)

(x + 1/x)2 = (3 + 2√(2) + 3 - 2√(2))2

x2 + 1/x2 + 2 = 62

x2 + 1/x2 = 36 - 2 = 34