Question

6. If x + y + z = 0, then (x + y)3 + (y + 2)3 + (z + x)3​

Answer 1

X+y+z = 0
X+y = -z
Y+z = -x
Z+x = -y
So (-y)3+ (-x)3 +(-z)3 =
- ( x3+y3+z3)
= -(3xyz) (x+y+z =0 x3 +y3 +z3 = 3xyz)