If $x+\frac{1}{x}=4$, then the value of $x^5+\frac{1}{x^5}$ is:
Answer & explanation
Correct answer: option 3
x5 + $\frac{1}{x^5}$ = (x2 + $\frac{1}{x^2}$) × (x3 + $\frac{1}{x^3}$) – (x + $\frac{1}{x}$)
If $x+\frac{1}{x}=4$,
If x + \(\frac{1}{x}\) = n
then, $x^3 +\frac{1}{x^3}$ = n3 - 3 × n
$x^3 +\frac{1}{x^3}$ = 43 - 3 × 4 = 52
If $K+\frac{1}{K}=n$
then, $K^2+\frac{1}{K^2}$ = n2 – 2
$x^2+\frac{1}{x^2}$ = 42 – 2 = 14
x5 + $\frac{1}{x^5}$ = 14 × 52 – 4 = 724