If x - = - 6, what will be the value of x5 - ?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. - 8886.
Given that
If x - = - 6
Squaring both sides
⇒ x2 + 1/x2 - 2 = 36
⇒ x2 + 1/x2 = 38
Now, x - = - 6
Cube both sides
⇒ x3 - 1/x3 - 3(x - 1/x) = - 216
⇒ x3 - 1/x3 = -216 - 18 = - 234
As we know,
⇒ x5 - = (x3 - 1/x3) (x2 + 1/x2) - ( x - )
= - 234 × 38 - (- 6) = - 8892 + 6 = - 8886