SSC CGL 2023 PYQ — Question 61

SSC CGL - 18 July 2023 - Shift 2 • Quantitative Aptitude • Q61

If x - 1x\frac{1}{x}= - 6, what will be the value of x5 - 1x5\frac{1}{x^5}?

Show answer & explanation

Correct answer: C

Explanation

The correct answer is option 3 i.e. - 8886.

Given that

If x - 1x\frac{1}{x}= - 6

Squaring both sides

⇒ x2 + 1/x2 - 2 = 36

⇒ x2 + 1/x2 = 38 

Now,  x - 1x\frac{1}{x}= - 6

Cube both sides

⇒ x3 - 1/x3 - 3(x - 1/x) = - 216

⇒ x3 - 1/x3 = -216 - 18 = - 234

As we know,

⇒ x5 - 1x5\frac{1}{x^5} = (x3 - 1/x3) (x2 + 1/x2) - ( x - 1x\frac{1}{x} )

= - 234 × 38 - (- 6) = - 8892 + 6 = - 8886