If x + y + z = 17, xyz = 171 and xy + yz + zx = 111, then the value of $$\root 3 \of {\left( {{x^3} + {y^3} + {z^3} + xyz} \right)} $$ is:
A. -64
B. 0
C. 4
D. -4
Answer: Option D
Solution(By Examveda Team)
x3 + y3 + z3 - 3xyz = (x + y + z)[x2 + y2 + z2 - (xy + yz + zx)](x + y + z)2 = x2 + y2 + z2 + 2(xy + yz + zx)
289 = x2 + y2 + z2 + 2 × 111
x2 + y2 + z2 = 67
Now,
x3 + y3 + z3 - 3xyz = 17(67 - 111)
x3 + y3 + z3 - 3xyz = -44 × 17
x3 + y3 + z3 - 3xyz + 4xyz = -748 + 4xyz
x3 + y3 + z3 + xyz = -748 + 4 × 171
x3 + y3 + z3 + xyz = -748 + 684
x3 + y3 + z3 + xyz = -64
$$\eqalign{ & \root 3 \of {\left( {{x^3} + {y^3} + {z^3} + xyz} \right)} \cr & = \root 3 \of { - 64} \cr & = - 4 \cr} $$
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