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Sunday, December 27, 2015

2015/114) Solve in real a^3 + b^3 = 8 – 6ab

a^3 + b^3 - 8 + 6ab = 0
or
a^3 + b^3 + (-2)^3 -3(-2)(a)(b) = 0
=> a + b – 2 = 0 or a=b= - 2
using the fact
x^3 + y^3 + z^3 – 3xyz = \dfrac{1}{2}(x+y+z)((x-y)^2 + (y-z)^2 + (z-x)^2)

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