Given a + B + C = 0, find the value of a (1b + 1c) + B (1c + 1a) + C (1a + 1b)

The original formula = AB + AC + BC + Ba + Ca + CB = B + Ca + A + CB + A + BC, from a + B + C = 0, B + C = - A, a + C = - B, a + B = - C, then the original formula = - 1-1-1 = - 3

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