verify that x^3+y^3+z^3_3xyz=1/2(x+y+z)(x_y)^2+(y_z)^2(z_x)^2
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x³ + y³ + z³ – 3xyz = 1/2 (x + y + z)[(x - y)² + (y - z)² + (z - x)²]
Using R.H.S
1/2 (x + y + z)[(x - y)² + (y - z)² + (z - x)²]
= 1/2 (x + y + z)[x² + y² - 2xy + y² + z² - 2yz + z² + x² - 2xz]
= 1/2 (x + y + z)[2x² + 2y² + 2z² - 2xy - 2yz - 2xz]
= 1/2 x 2 (x + y + z)[x² + y² + z² - xy - yz - xz]
= (x + y + z)[x² + y² + z² - xy - yz - xz]
= x³ + xy² + xz² - x²y - xyz - x²z + yx² + y³ + yz² - xy² - y²z - xyz + zx² + zy² + z³ - xyz - yz² - xz²
= x³ + y³ + z³ - 3xyz = L.H.S
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