Question

If a + b = 8 and ab = 6, find the value of a3 + b3.

Answer 1

a + b = 8, ab = 6

Cubing both sides of a + b = 8, we get

(a + b)3 = (8)3

a3 + b3 + 3ab(a + b) = 512

a3 + b3 + 3 x 6 x 8 = 512

a3 + b3 + 144 = 512

a3 + b3 = 512 – 144 = 368

a3 + b3 = 368