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SSC CHSL 2019 PYQ — Question 70

SSC CHSL - 5th July 2019 - Shift 1 • Quantitative Aptitude • Q70

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if x4+ x-4 = 1442, (x > 0) then the value of x + x-1 is:

Show answer & explanation

Correct answer: B

Explanation

Correct Answer is option 2 i.e. 2√10

Understanding Application

If

a2 + 1/a2 = p

then

a + 1/a = √(p + 2)

Given
x4 + 1/x4 = 1442, (x > 0)

x4 + 1/x4 = 1442

Then

x2 + 1/x2 = √(1442 + 2)

x2 + 1/x2 = √1444 = 38

Now,

x + 1/x = √(38 + 2)

= √40

= 2√10