1, ab + ac = a(b+c)
2, ab - ac + ad = a(b-c+d)
3, ax-bx-cx+dx = x(a-b-c+d)
4, a(b+c) - d(b+c) = (a-d)(b+c)
5, ac-ad+bc-bd = a(c-d) + b(c-d) = (a+b)(c-d)
6, ax+by+bx+ay=ax+ay+bx+by=a(x+y)+b(x+y)=(a+b)(x+y)
a(b+c)
a(b-c+d)
x(a-b-c+d)
(b+c)(a-d)
a(c-d)+c(c-d)=(c-d)(a+c)
a(x+y)+b(x+y)=(x+y)(a+b)
T