Coordinate Geometry

Question

 If x + y + z = 0, show that x3 + y3 + Z3 = 3xyz.

Answer

We know that
x3 + y3 + z3 - 3xyz
= (x + y + z)(x2 + y2 + z- xy - yz - zx)
| Using Identity VIII
= (0)(x2 + y2 + z2 - xy - yz - zx)
| ∵ x + y + z = 0
= 0
⇒ x3 + y3 + z3 = 3xyz.

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