Practicing Success
If $x = \sqrt[3]{5} + 2 $, then the value of $x^3 = 6x^2 + 12 x- 12$ is equal to: |
0 2 1 -1 |
1 |
(a - b)3 = a3 - b3 - 3ab(a-b) If $x = \sqrt[3]{5} + 2 $, then the value of $x^3 = 6x^2 + 12 x- 12$ If $x = \sqrt[3]{5} + 2 $ = x - 2 = $ \sqrt[3]{5}$ = (x - 2)3 = 5 x3 - 6x2 + 12x - 8 = 5 ⇒ x3 - 6x2 + 12x - 13 = 0 ⇒ x3 - 6x2 + 12x - 13 + 1 = 1 ⇒ x3 - 6x2 + 12x - 12 = 1 |