解下列方程：
（1）x2+2x-15=0
（2）（x+4）2=5（x+4）
（3）x2-1=4x
（4）2x（x-1）=3x-2．
（1）∵x2+2x-15=0，
∴（x+5）（x-3）=0，
即：x+5=0或x-3=0，
解得：x1=-5，x2=3；
（2）∵（x+4）2=5（x+4），
∴（x+4）（x+4-5）=0，
即x+4=0或x+4-5=0，
解得：x1=-4，x2=1；
（3）∵x2-1=4x，
∴x2-4x=1，
∴x2-4x+4=1+4，
∴（x-2）2=5，
∴x-2=±
，5
解得：x1=2+
，x2=2-5
；5
（4）∵2x（x-1）=3x-2，
∴2x2-2x-3x+2=0，
∴2x2-5x+2=0，
∴（2x-1）（x-2）=0，
即2x-1=0或x-2=0，
解得：x1=
，x2=2．1 2
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| It took George quite a while to find a 1 place for his car and in the end he had to leave it in a narrow street, 2 from the dentist's. As he got out, he glanced at his 3 . His appointment(约会)was at five and he still had twenty minutes to 4 . He crossed into the square and 5 on a bench, partly to 6 the last of the atternoon sun, 7 to calm his nerves(神经). He hated these visits 8 the dentist(牙医). As he sat there, watching the children at play and 9 to the old women talking to each other, he turned around to see a red car like his own come out of the 10 where he had parked. The car gathered speed and was soon 11 of sight. George 12 in his pockets for the keys: They were not there. "My car!" he cried 13 a loud voice, which made several people stare at him. He got up and ran across the 14 and then down the narrow street. His car was not to be seen-but then he discovered it concealed (被隐藏) 15 a large one. He was relieved (使宽慰) to find his 16 , still in his car. By the time he reached the dentist's it was already five. "I had rather an odd (奇特的) 17 ," he said to the dentist to explain his 18 "I thought my car had been 19 " "It's quite 20 sir," said the dentist. "As a matter of fact I have only just got here myself." | ||||
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