6x^2+7xy+2y^2-8x-5y+2
=(2x+y)(3x+2y)-8x-5y+2
下面我们用待定系数法来解答
(2x+y)(3x+2y)-8x-5y+2=（2x+y+m)(3x+2y+n)
=6x^2+7xy+2y^2+(3m+2n)x+(n+2m)y+mn
mn=2
3m+2n=-8
n+2m=-5
n=-1
m=-2
(2x+y)(3x+2y)-8x-5y+2=（2x+y-2)(3x+2y-1)