3X^2+5xy-2Y^2+X+9y-6=（3X+Y)(X-2Y)+X+9y-6=（3X-Y+a)(X+2Y+b)aX+3bX=Xa+3b=1 (1)2aY-bY=9y2a-b=9 (2)由(1)(2)式解得a=4,b=-1ab=-4不好意思,题目是不是错了,麻烦检查下3X^2+5xy-2Y^2+X+9y-4=（3X-Y+4)(X+2Y-1)...