If a + b = 3, then the value of a3 + b3 + 9ab is
27
9
16
16
A.
27
a + b = 3
On cubing both sides,
(a + b)3 = (3)3
a3 + b3 + 3ab(a + b) = 27
a3 + b3 + 3ab x 3 = 27
∴ a3 + b3 + 9ab = 7
If x = 222, y = 223, z = 225, then the value of x3 + y3 + z3 - 3xyz
4590
4690
4950
4950