Practicing Success
If $x^2+\frac{1}{x^2}= 18,x > 0$, then find the value of $x^3+\frac{1}{x^3}$. |
52 $17\sqrt{5}$ $34\sqrt{5}$ $46\sqrt{5}$ |
$34\sqrt{5}$ |
If $(x^2+\frac{1}{x^2}) = 18, x > 0 $ $(x^3+\frac{1}{x^3})$= ? If $K^2+\frac{1}{K^2}$ = n then, K+ \(\frac{1}{k}\) = \(\sqrt {n + 2}\) x+ \(\frac{1}{x}\) = \(\sqrt {18 + 2}\) = 2\(\sqrt {5}\) $(x^3+\frac{1}{x^3})$= (2\(\sqrt {5}\)) 3 - 3 × 2\(\sqrt {5}\) = $40\sqrt{5}$ - $6\sqrt{5}$ = $(x^3+\frac{1}{x^3})$ = $34\sqrt{5}$ |