题目

My friends and I finished lunch at a hotel when it started to rain heavily. When it became lighter, I decided to get my car at my office three streets away.My friends said that I shouldn’t go, mainly because I would give birth to a new baby and was seven months pregnant then. I told them that I’d be very careful. One of them wanted to come with me but I asked her to stay with another friend who needed help with her baby.I walked out of the hotel and started making my way to the car. At the crossing, a black car stopped and a man came out with an umbrella. Before I knew what was happening, 当-1≤x≤2时，函数y=2x2-4ax+a2+2a+2有最小值2．求a所有可能取的值．