Practicing Success
If x2 - 21x - 1= 0 and x > 1, then the value of x3 - \(\frac{1}{x^3}\) will be: |
8723 9324 9867 8943 |
9324 |
If x2 - 21x - 1= 0 Divide by x on both sides, x - \(\frac{1}{x}\) = 21 x3 - \(\frac{1}{x^3}\) = 213 + 3 × 21 = 9324
Note - if x - \(\frac{1}{x}\) = a then x3 - \(\frac{1}{x^3}\) = a3 + 3a |