Practicing Success
x2 + \(\frac{1}{x^2}\) = 98 (x > 0), then find the value of x5 + \(\frac{1}{x^5}\). |
95060 95070 95050 95080 |
95050 |
x2 + \(\frac{1}{x^2}\) = 98 (x + \(\frac{1}{x}\)) = \(\sqrt {98\;+\;2}\) = 10 x3 + \(\frac{1}{x^3}\) = 1000 - 3(10) = 970 Now, x5 + \(\frac{1}{x^5}\) = (x2 + \(\frac{1}{x^2}\)) (x3 + \(\frac{1}{x^3}\)) - (x + \(\frac{1}{x}\)) = (98 × 970) - 10 = (100 × 970) - (2 × 970) - 10 = 97000 - 1940 - 10 = 97000 - 1950 = 95050 |