SSC Selection Post 2019 PYQ — Question 53

SSC Selection Post - Higher Secondary Level 2019 - 15 Oct 2019 • Quantitative Aptitude • Q53

If x4 + 1x4{1 \over x^4} = 2, and x is a positive quantity, then x is equal to: 

Show answer & explanation

Correct answer: A

Explanation

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

Given,  x4 + 1x4{1 \over x^4} = 2

⇒ x4+1x4+2=4x^4 + \frac{1}{x^4} + 2 = 4

⇒ x2+1x2=2x^2 + \frac{1}{x^2} = 2

Also, x2+1x2+2=4x^2 + \frac{1}{x^2} + 2 = 4

⇒ x+1x=2x + \frac{1}{x} = 2

⇒ x2 - 2x + 1 = 0

⇒ (x - 1)(x - 1) = 0

⇒ x = 1