数学问题:分解因式

思路：先乘起来 合并同类项以后再分解因式
原式=(5ax-5bx+5cx+5ay-5by+5cy)+(3bx-3ax-3cx+3by-3ay-3cy)
=2ax-2bx+2cx+2ay-2by+2cy
=2x(a-b+c)+2y(a-b+c)
=2(x+y)(a-b+c)

(a-b+c)(5x+5y-3x+3y)=(a-b+c)(2x+8y)

原式=5(x+y)(a-b+c)-3(x-y)(a-b+c)
=(5x+5y-3x+3y)(a-b+c)
=(2x+8y)(a-b+c)
=2(x+4y)(a-b+c)

2xa+8ya-2xb-8yb+2xc+8yc