b²-4ac=(m-1)²-4>=0∴m²-2m-3>=0(m-3)(m+1)>=0∴ m>=3或m<=-1
有两个实数根：Δ=(-(m-1))²-4*1*1=m²-2m-3>0(m-3)(m+1)>0m<-1或者m>3
