已知二次函数y=a(x-m)²-2a(x-m)（a,m为常数，且a≠0）.
（1）求证：不论a与m为何值，该函数的图象与x轴总有两个公共点；
（2）设该函数的图象的顶点为C，与x轴交于A，B两点，当△ABC是等腰直角三角形时，求a的值．

094型导弹核潜艇是中国最先进的战略核潜艇，水下最大航速为45节（1节=1.852km/h），核反应堆最大输出功率为4.5万千瓦，最大续航里程为20万海里（1海里=1.852km）．假设1个 ${}_{92}^{235}$ U核裂变放出能量是200MeV，铀矿石含铀235的浓度是4%，求：

①实行中央集权的政治制度

②加强各民族之间的联系

③结束分裂局面实线大一统

④由少数民主建立的政权

    Katie was in big trouble．She was such a sweet kid; a third-grade teacher always dreamed of having a classroom filled with Katies, she was never ever a discipline（纪律） problem. I just couldn't imagine why she had made her parents so angry．

    It seemed that Katie had been spending money in the lunchroom. Her parents explained that Katie brought a great homemade lunch each day, and there was no reason for her to buy school lunch. They wondered why but failed．So they asked me to help them get to the bottom of this situation.

    The next day, I asked Katie to my office. “Why are you buying lunches, Katie? What happened to your homemade lunch?” I asked. “I lose it,” she replied. “I don't believe you, Katie. Is someone stealing your lunch, Katie?” I asked. “No. I just lose it,” she said．Well, there was nothing else I could do．

    The problem was still unsolved the next week when I noticed a boy who was new to the school sitting alone at a lunch table. He always looked sad and scared. I thought I would go and sit with him for a while. As I walked towards him, I noticed the lunch bag on the table. The name on the bag said “Katie”.

    Now I understood and I talked to Katie. It seemed that the new boy never brought a lunch, and he wouldn't go to the lunch line for a free lunch. He had told Katie his secret and asked her not to tell anyone that his parents wanted him to get a free lunch at school. Katie asked me not to tell her parents, but I drove to her house that evening after I was sure that she was in bed. I had never seen parents so proud of their child.

    Katie still buys lunch every day at school. And every day, as she heads out of the door, her  mom hands her a delicious homemade lunch．