问题
解答题
已知a、b、c为△ABC的三边，且满a2c2-b2c2=a4-b4，则△ABC的形状为______．
答案
∵a2c2-b2c2=a4-b4
∴（a2-b2）c2=（a2-b2）（a2+b2）
∴（a2-b2）（a2+b2-c2）=0
∴a2-b2=0，a2+b2-c2=0
∴a2=b2，a2+b2=c2
∴△ABC的形状为等腰三角形或直角三角形．
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已知a、b、c为△ABC的三边，且满a2c2-b2c2=a4-b4，则△ABC的形状为______．
∵a2c2-b2c2=a4-b4
∴（a2-b2）c2=（a2-b2）（a2+b2）
∴（a2-b2）（a2+b2-c2）=0
∴a2-b2=0，a2+b2-c2=0
∴a2=b2，a2+b2=c2
∴△ABC的形状为等腰三角形或直角三角形．
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| A boy who was cleaning shoes in the street said to a young man 1 by, "Let me clean your shoes, 2 ?" The young man said, "No, thank you." "You may 3 me only a pound for that, sir." said the boy. 4 the young man refused again. Then the boy told him that he would clean his shoes for 5 . The young man agreed to this, and soon one of his shoes was shining brightly. The man put 6 shoe on the boy, but the boy refused to clean it unless he 7 two pounds for his work. The young man refused to pay anything and went away. But one looked 8 dirty that he couldn't walk away. He had to 9 and gave the boy 10 . In a very short time his shoes shone brightly. | ||||
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