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
完形填空。 | ||||
| A student was one day taking a walk with a professor. He was __1__ called the students' friend, for his kindness to those who waited on his __2___. As they went along, they saw lying in the path a pair of old shoes, which they supposed to belong to a poor man who was employed in a field close by, and who had __3___ finished his day's work. The student turned to the professor, saying: "Let us play the man a__4__: we will hide his shoes, and wait to see his___5___when he cannot find them." "My young friend," answered the professor, "we__6___ never amuse ourselves ___7___ the poor. But you are rich, and may give yourself a much greater__8___ by means of the poor man. Put a coin into each shoe, and __9__ watch how the discovery affects him." The student did so, and they both placed themselves behind the bushes close by. The poor man soon finished his work, and came 10 the field to the path where he had left his coat and shoes. While putting on his coat he __11___ his foot into one of his shoes; but feeling something __12___, and then he found the coin. __13___and wonder were seen upon his face. He gazed upon the coin, __14__ it round, and looked at it again and again. He then looked around but no person was to be seen. And his surprise was __15___ on finding the other coin. His __16__ overcame him; he fell upon his knees, __17__ to heaven and uttered aloud a passionate thanksgiving, __18__ he spoke of his wife, sick and helpless, and his children without bread, whom the __19__ money, from some unknown hand, would save from dying. The student stood there deeply affected, and his eyes filled with tears, "I feel now the __20__ of those words, which I never understood before: 'It is more blessed to give than to receive.'" | ||||
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