Question

1、x-y-x+y 2、a-4a+4-9b 3、4x-a-6a-9 4、已知x-y+x+y=（x+y）·A,则A= 5、

Answer 1

1、x-y-x+y=(x-y)(x+y)-(x-y)=(x-y)(x+y+1) ; 2、a-4a+4-9b=(a-2)-9b =(a-2-3b)(a-2+3b); 3、4x-a-6a-9=4x -(a+3)=(2x-a-3)(2x+a+3); 4、x-y+x+y==(x-y)(x+y)+(x-y)=(x-y+1)(x+y) x-y+1=A 5、x-y-2y-1=x-(y+1)=(x-y-1)(x+y+1)