If x - \(\frac{1}{x}\) = 4\(\sqrt{2}\)
then find the value of x3 + \(\frac{1}{x^3}\)
Answer & explanation
Correct answer: option 3
⇒ If x - \(\frac{1}{x}\) = a then x + \(\frac{1}{x}\) = \(\sqrt {a^2 + 4}\)
and
If x + \(\frac{1}{x}\) = a then ⇒ x3 + \(\frac{1}{x^3}\) = a3 - 3a
ATQ,
x - \(\frac{1}{x}\) = 4\(\sqrt{2}\), then
⇒ x + \(\frac{1}{x}\) = \(\sqrt {(4\sqrt{2})^2 + 4}\) = 6
⇒ x3 + \(\frac{1}{x^3}\) = 63 - 3 × 6 = 198