If x + y + z = 6 and x2 + y2 + z2 = 20, then the value of x3 + y3 + z3 - 3xyz is
64
70
72
76
If a3 - b3 - c3 = 0, then the value of a9 - b9 - c9 - 3a3b3c3 is
1
2
0
-1
C.
0
Given expression,
a3 - b3 - c3 = 0,
⟹ a3 = b3 + c3 ...(i)
On cubing both sides, we get
(a3)3 = (b3 + c3)3
a9 = b9 + c9 + 3b3c3(b3 + c3)
a9 = b9 + c9 + 3b3c3a3
⟹ a9 - b9 - c9 - 3a3b3c3 = 0