x+y+ax+ay=（x+y)(a+1)bx+by+ax+ay=(x+y)(a+b)x ² -y ² +x+y=(x+y)(x-y+1)2a+4+3ab+6b=2(a+2)+3b(a+2)=(3b+2)(a+2)a ² +2ab+b ² -1=(a+b+1)(a+b-1)1-x ² -2xy-y ²=(1-x-y)(1+x+y)