A∩B=A,那么A是B的子集.(1)a>0时,B={x|-1/a<=x<=2/a}有-1/a<=-1,2<=2/a得:0(2)a<0时,B={x|2/a<=x<=-1/a}有:2/a<=-1,2<=-1/a得-1/2<=a<0(3)a=0时,B=R.符合.综上所述范围是-1/2<=a<=1.