x²-xy-6y²²+2x-y+k
=(x-3y)(x+2y)+2x-y+k
则应等于(x-3y+a)(x+2y+b)
(x-3y+a)(x+2y+b)
=(x-3y)(x+2y)+(a+b)x+(2a-3b)t+ab
=(x-3y)(x+2y)+2x-y+k
所以a+b=2
2a-3b=-1
k=ab
所以a=1,b=1
所以k=ab=1