Practicing Success
If a + b + c = 11, ab + bc + ca = 3 and abc = —135, then what is the value of a3 + b3 + c3 ? |
925 827 929 823 |
827 |
a + b + c = 11, ab + bc + ca = 3 abc = -135 a3 + b3 + c3 – 3abc = (a + b + c) [(a + b + c)2 – 3(ab + bc + ca)] = a3 + b3 + c3 – 3 × (-135) = 11 [112 – 3 × 3] = a3 + b3 + c3 + 405 = 11 × [121 – 9] = a3 + b3 + c3 = 1232 – 405 = a3 + b3 + c3 = 827 |