>>885
与式
=(b^2-c^2)a^3-(b^3-c^3)a^2+b^3c^2-b^2c^3
=(b-c)(b+c)a^3-(b-c)(b^2+bc+c^2)a^2+(b-c)b^2c^2
=(b-c){(a+c)a^3-(b^2+bc+c^2)a^2+b^2c^2}
=(b-c)(a-b)(a-c){(b+c)a+bc}
=-(a-b)(b-c)(c-a)(ab+bc+ca)