mx^2+(m-2)x+1=0存在正根
(1)m=0时,-2x+1=0,x=1/2符合.
(2)m不=0时,判别式=(m-2)^2-4m>=0
m^2-8m+4>=0
(m-4)^2>=12
m>=4+2根号3或m=4+2根号3或m