Question 41

If $$x + \frac{1}{x} = 1$$, then find the value of $$x^3 + \frac{1}{x^3}$$.

Solution

$$x+\frac{1}{x}=1.$$

So, $$x^3+\frac{1}{x^3}=\left(x+\frac{1}{x}\right)\left(x^2-x\ .\frac{1}{x}+\frac{1}{x^2}\right)=1.\left(\left(x+\frac{1}{x}\right)^2-1-2.x\ \frac{1}{x}\right)=1^2-1-2=-2.$$

D is correct choice.


Create a FREE account and get:

  • Download RRB Study Material PDF
  • 45+ RRB previous papers with solutions PDF
  • 300+ Online RRB Tests for Free

cracku

Boost your Prep!

Download App