1若分解x2xm得到两个因式x2与xn的积求m和n的值(x-2)(x-n)=x2-(2+n)x+2n=x2-x+m所以-(2+n)=-12n=m所以n=-1,m=-2(x-2)(x-n)=x2-(2+n)x+2nx2-x+m=x2-(2+n)x+2n1=2+nm=2n解得n=-1;m=-22，因式分解1x22x12x22xyy23x2y2（x2－2x）2＋2（x2－2x）＋1=（x^2-2x+1)^2=(x-1)^4x2＋2xy＋y2－1=(x+y)^2-1=(x+y+1)(x+y-1)x2－y2=(