1)(m-n)(m+n)-(m-n)=(m-n)(m+n-1)
2)(3x-2y)(3x+2y)-(3x-2y)=(3x-2y)(3x+2y-1)
3)x²(x+3)-4(x+3)=(x+3)(x²-4)=(x+3)(x-2)(x+2)
4)(9-3+8y)(9+3-8y)=(5+8y)(12-8y)
5)(x+5-4)(x+5+4)=(x+1)(x+9)
6)(6-y-1)(6+y+1)=(5-y)(7+y)
7)(3x-7-5)(3x-7+5)=(3x-12)(3x-2)=3(x-4)(3x-2)
8)(4-5x-8)(4-5x+8)=(-5x-4)(12-5x)=(5x+4)(5x-12)