1.xy-xz+y-z
=x(y-z)+(y-z)
=(y-z)(x+1)
2.a^2+ab+ac+bc
=a(a+b)+c(a+b)
=(a+b)(a+c)
3.ax-2bx+ay-2by
=x(a-2b)+y(a-2b)
=(a-2b)(x+y)
4.4xy-3xz+8y-6z
=x(4y-3z)+2(4y-3z)
=(4y-3z)(x+2)
5.x^3+3x^2+3x+9
=x^2(x+3)+3(x+3)
=(x+3)(x^2+3)
6.3xy-2x-12y+8
=x(3y-2)-4(3y-2)
=(3y-2)(x-4)
7.ab-5bc-2a^2+10ac
=a(b-2a)-5c(b-2a)
=(b-2a)(a-5c)
8.5ax+7ay-5bx-7by
=a(5x+7y)-b(5x+7y)
=(5x+7y)(a-b)
9.x^3 y+3x-2x^2 y^2-6y
=x(x^2y+3)-2y(x^2y+3)
=(x^2y+3)(x-2y)
10.x^2-a^2-2x-2a
=(x+a)(x-a)-2(x-a)
=(x-a)(x+a-2)
11.x^3+x^2 y -xy^2-y^3
=x^2(x+y)-y^2(x+y)
=(x+y)(x+y)(x-y)
12..x^2-y^2+ax+ay
=(x+y)(x-y)+a(x+y)
=(x+y)(x-y+a)
13.x^2-x-9y^2-3y
=(x+3y)(x-3y)-(x+3y)
=(x+3y)(x-3y-1)
14.a^2-b^2+4b-4
=a^2-(b-2)^2
=(a+b-2)(a-b+2)
15.a^2-2ab+b^2-c^2
=(a-b)^2-c^2
=(a-b-c)(a-b+c)
16.x^2-y^2-z^2+2yz
=-(y-z)^2+x^2
=(y-z-x)(y-z+x)
17.9-4a^2-4ab-b^2
=9-(2a+b)^2
=(3+2a+b)(3-2a-b)
18..-1-2x-x^2+y^2
=y^2-(x+1)^2
=(y+x+1)(y-x-1)
