SSC CGL 2021 PYQ — Question 65

The correct answer is Option 1 i.e  $8\sqrt11$.

 x² - $\sqrt 11x+1=0$

on dividing by x on both sides one gets,

⇒ x + 1/x - $\sqrt 11$ = 0

⇒ x + 1/x = $\sqrt 11$

On cubing both side we get

 ⇒ (x + 1/x)³ = $(\sqrt 11)^3$

 ⇒ x³ + 1/x³ + 3 × $\sqrt 11$ = 11$\sqrt 11$

  ⇒ x³ + 1/x³ = 8$\sqrt 11$.