x3 + y3 + z3 = 3xyz
x3 + y3 + z3 – 3xyz = 0
x3 + y3 + z3 – xyz – xyz – xyz = 0
x3 + y3 + z3 – xyz – xyz – xyz - x2y – y2x – x2z – z2x - y2z – z2y + x2y + y2x + x2z + z2x + y2z+ z2y = 0
(x3 + x2y + x2z) + (y3 + y2x + y2z) + (z3 + z2x + z2y) – ( xyz + x2y + y2x) - (xyz + x2z + z2x) - (xyz + z2y + y2z) = 0
( x + y + z ) ( x2 + y2 + z2 – xy – xz – yz) = 0 ó ( x + y + z )( x – y)2(y – z)2(z – x)2 = 0
=> x + y + z = 0 hoặc x = y = z
mà theo đề ra thì x + y + z \(\ne\)0 nên x = y = z
vậy P = ..............
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