x^2-2mx=-m^2+2x
x^2-2(m-1)x+m^2=0
△=[-2(m-1)]^2-4*1*m^2
=4m^2-8m+4-4m^2
=4(1-2m)
x1+x2=2(m-1)
|x1|=x2
1）当x10时
x1=x2
△=0
4(1-2m)=0
1-2m=0
m=1/2