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If x + y + z = 9 and xy + yz + zx = 20, find the value of x^3 + y^3 + z^3 - 3xyz.

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If x + y + z = 9 and xy + yz + zx = 20, find the value of x^3 + y^3 + z^3 - 3xyz.
posted Jan 8, 2020 by Vishal

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1 Answer

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(x + y + z)^3 = x^3 + y^3 + z^3 + 3[(x + y + z)(xy +xz + yz)] - 3xyz
(x + y + z)^3 - 3[(x+y+z)(xy + yz + zx)] = x^3 + y^3 + z^3 - 3xyz
(9)^3 - 3(9)(20) = 189.

answer Jan 8, 2020 by Tejas Naik



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