1) 2ax+3by+6ay+bx=
2ax+6ay+3by+bx=
=2a(x+3y)+b(3y+x)=
=(x+3y)(2a+b)
2)3c+3c²-a-ac=
=3c(1+c)-a(1+c) = (1+c)(3c-a)
3)ax+bx+cx+ay+by+cy=
=x(a+b+c)+y(a+b+c) = (a+b+c)(x+y)
4)ay-12bx+3ax-4by=
=ay+3ax-12bx-4by=
=a(y+3x)-4b(3x+y)=
=(y+3x)(a-4b)
5)a²b²+ab+abc+c = ab(ab+1)+c(ab+1) = (ab+1)(b+c)
6)ab-a²b²-a³b³-c+abc-ca²b²=ab(1-ab+a²b²)-c(1-ab+a²b²)=
=(1-ab+a²b²)(ab-c)