原式=(x+y)(x-y)+mx+5y-6设原式=(x+y+a)(x-y+b)=(x+y)(x-y)+(a+b)x+(b-a)y+ab所以m=a+b5=b-a-6=ab则b=a+5-6=a(a+5)a²+5a+6=0(a+2)(a+3)=0a=-2,a=-3b=a+5=3,2即a=-2,b=3a=-3,b=2所以m=1或-1