A = (a-b)(b-c)(a-c)+(a+b)(c+a)(c-b)+(b+c)(c+a)(b-a)
= ( b - c)($a^{2} - ab - ac + bc - ac - bc - a^{2} - ab )+ (b + c)(c + a)(b - a)$
= -2a.(b + c) (b - c) + (b+c)(c+a)(b-a)
= ( b + c ) ( bc + ab - ac - $a^{2}$ - 2ab + 2ac )
= ( b + c ) ( bc - ab + ac - $a^{2}$ )
= ( b + c ) ( a + b ) ( c - a )