1 2-[(x+3)/(x+1)]≥0 x-1/x+1≥0 -1＜x≤12 (x-a-1)(2a-x)＞0 [x-(a+1)](x-2a)＜0 2a＜x＜a+1 ∵B∈A ∴2a≥-1且a+1≤1 a≥-0.5且a≤0 ∴-0.5≤a≤0
