6x²+xy-2y²+2x-8y-8=0
(3x+2y)(2x-y)+2x-8y-8=0
(3x+2y+4)(2x-y-2)=0
3x+2y+4=0
2x-y-2=0
解得：x=0
y=-2(3x+2y+4)(2x-y-2)=0咋得来的？十字相乘法：3x+2y4 ╳2x-y-2