x²-2mx+2m-4=0
a=1 b=-2m c=2m-4
判别式△=b²-4ac
=4m²-4(2m-4)
=4m²-8m+16
=4(m²-2m+1)+12
=4(m-1)²+12>0
∴无论m取何值,方程总有两个不相等的实根