4-m²+2m-1
=4-(m²-2m+1)
=2²-(m-1)²
=[2+(m-1)][2-(m-1)]
=(2+m-1)(2-m+1)
=(m+1)(3-m)a²-b²-2b-19x²-y²-4y-4谢谢你的提示，我又做了这两题，麻烦您做一下和我对下答案可以吗？a²-b²-2b-1=a²-(b²+2b+1)=a²-(b+1)²=[a+(b+1)][a-(b+1)]=(a+b+1)(a-b-1)9x²-y²-4y-4=9x²-(y²+4y+4)=9x²-(y+2)²=[3x+(y+2)][3x-(y+2)]=(3x+y+2)(3x-y-2)有思考，就有进步，祝你成功！