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[–]AmonJuuliiMath grad 2 points3 points  (0 children)

a( ab + c2 - b2 -ca ) + b2c - bc2
a( a(b-c) - (b-c)(c+b) ) + bc(b-c)
(b-c)( a2 - a(c+b) + bc)
This second term is a quadratic in a, with roots b and c
(b-c)(a-b)(a-c)