2(b−c)+b2(c−a)+c2(a−b)a2(b−c)+b2(c−a)+c2(a−b)
=a2(b−c)−b2[(b−c)+(a−b)]+c2(a−b)=a2(b−c)−b2[(b−c)+(a−b)]+c2(a−b)
=a2(b−c)−b2(b−c)−b2(a−b)+c2(a−b)=a2(b−c)−b2(b−c)−b2(a−b)+c2(a−b)
=(a2−b2)(b−c)−(b2−c2)(a−b)=(a2−b2)(b−c)−(b2−c2)(a−b)
=(a−b)(a+b)(b−c)−(b−c)(b+c)(a−b)=(a−b)(a+b)(b−c)−(b−c)(b+c)(a−b)
=(a−b)(b−c)(a+b−b−c)=(a−b)(b−c)(a+b−b−c)
=(a−b)(b−c)(a−c)