(1)
=a²(b-c)+b²c-b²a+c²a-c²b
=(b-c)a²-(b²-c²)a+b²c-c²b
=(b-c)a²-(b+c)(b-c)a+bc(b-c)
=(b-c)(a²-(b+c)a+bc)
=(b-c)(a-b)(a-c)
=(a-b)(b-c)(a-c)
(2)
=(ab+ac+b²+bc)(c+a)+abc
=abc+ac²+b²c+bc²+a²b+a²c+b²a+abc+abc
=a²b+a²c+ab²+3abc+ac²+b²c+bc²
=(b+c)a²+(b²+2bc+c²+bc)a+bc(b+c)
=(b+c)a²+{(b+c)²+bc}a+bc(b+c)
={(b+c)a+bc}{a+(b+c)}
=(ab+bc+ca)(a+b+c)