If x + 1/x = 3, then what is the value of x³ + 1/x³?
- 18
- 20
- 21
- None of these
Explanation
Given x + 1/x = 3
To find x³ + 1/x³:
(x + 1/x)³ = x³ + 3(x²)(1/x) + 3(x)(1/x)² + 1/x³
= x³ + 3x + 3/x + 1/x³
= x³ + 1/x³ + 3(x + 1/x)
(x + 1/x)³ = x³ + 1/x³ + 3(3)
27 = x³ + 1/x³ + 9
x³ + 1/x³ = 27 - 9
= 18
Related MCQs
- (x+5)(x−4)/(x−2)(x+2)
- x+5/x+2
- x−4/x−2
- x+5/x−2
اس سوال کو وضاحت کے ساتھ پڑھیں
- 20
- 25
- 30
- 35
اس سوال کو وضاحت کے ساتھ پڑھیں
