ax+ay+az=
-ax-bx-cx=
ax+bx-ay-by=
1.ax+ay+az=a(x+y+z)
2.-ax-bx-cx=-x(a+b+c)
3.(x-y)(a2-ab+b2)
4.ax+bx-ay-by=x(a+b)-y(a+b)=(a+b)(x-y)