(m+1)x2 -mx+m-1=0有实数根时,m的取值范围是集合A
如果m=-1 那么方程是x-2=0有实数根
如果m≠-1 方程有实数根△=m²-4（m+1）（m-1）=m²-4m²+4=4-3m²>=0
-2根号3/3<=m<=2根号3/3 且m不等于-1
综上A={-2根号3/3<=m<=2根号3/3}
B不完整,没法解