已知△ABC三个顶点坐标分别为A（1，2），B（3，1），C（-1，-1）．
（1）求BC边上的高线所在的直线方程；
（2）求BC边上的中线所在的直线方程．
（1）由题意可得直线BC的斜率kBC=
=-1-1 -1-3
，1 2
∴BC边上的高线所在的直线的斜率为-2，
∴所求直线的方程为：y-2=-2（x-1），
化为一般式可得：2x+y-4=0
（2）∵B（3，1），C（-1，-1），
∴BC的中点D的坐标为（1，0），
∴BC边上的中线所在的直线方程为：x=1
阅读下面短文，根据短文内容完成表格中所缺信息，每空一词。（共10小题，每小题1分，计10分） March 25 is the 17th National Day of Education on the Safety of Elementary and Middle School Students. The theme of the day this year is to give students more knowledge about how to keep safe. How can you keep yourselves safe? Here are some suggestions. When there is a fire: Shout out “Fire”! Call 119! Try to find a safe exit and get away quickly. Don’t use a lift. Use a piece of cloth to cover your mouth and nose. When there is an earthquake at school: Stay calm. Follow the teachers’ instructions. Quickly move under the desk. Don’t jump out of windows or run out. When you are on the street: Wait for the green traffic light. Look left and right before crossing the street. Don’t run across the street. When you are eating: Wash fruits and vegetables carefully before eating them. Check the expiration dates(保质期) of the food. Don’t eat the food if it looks or smells bad. When you are at school: Take care not to fall down or hurt yourself. Don’t run, jump or push while going upstairs or downstairs. Take care of yourself all the time.
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