问题
计算题
计算：（1）（2x）3×（﹣3xy2）
（2）（a+3b）（a﹣2b）﹣（2a﹣b）2．
答案
解：（1）原式=8x3×（﹣3xy2）=﹣24x4y2；
（2）原式=a2﹣2ab+3ab﹣6b2﹣（4a2﹣4ab+b2）
=a2﹣2ab+3ab﹣6b2﹣4a2+4ab﹣b2
=﹣3a2+5ab﹣7b2．
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计算：（1）（2x）3×（﹣3xy2）
（2）（a+3b）（a﹣2b）﹣（2a﹣b）2．
解：（1）原式=8x3×（﹣3xy2）=﹣24x4y2；
（2）原式=a2﹣2ab+3ab﹣6b2﹣（4a2﹣4ab+b2）
=a2﹣2ab+3ab﹣6b2﹣4a2+4ab﹣b2
=﹣3a2+5ab﹣7b2．
| 完形填空。 | ||||
| It was a cold, wet day on June 6, 2010, when 14-year-old Wasana arrived at school. Waiting outside his classroom for his classmates to 1 , Wasana stared at the 2 . Then his eyes fell upon the 18-metre-high hill that 3 at the back of the classroom. He 4 large amounts of rainwater flowing down the hill, and water was also bubbling (冒泡) at the base of a rock on the hill. For a few minutes, Wasana 5 the water, wondering why it looked so 6 . Then it hit him - the 7 was similar to the video he was shown during Disaster Management classes. Fearing a 8 disaster, he shouted 9 at the students waiting outside their classrooms."Run, run, don't stay here! The 10 on the hill is going to fall on us!" Chaos (混乱) broke out 11 the students ran to the open area that had been appointed as an emergency gathering point. When some teachers 12 Wasana, he showed them the water rushing down the hill, and they started leading the students to safer ground. Just then headmaster Gurusinghe drove into the school. Wasana ran over to tell him what was happening. After 13 the site (现场), Gurusinghe knew the school was in 14 . The enormous rock at the top of the hill could come crashing down 15 . 16 a group of teachers and older students, Gurusinghe climbed the hill and tried to make the water flow away from the rock. They were too 17 . Ten minutes later, they heard screams as the huge rock rushed down the hill. There was little Gurusinghe and his group could do as they watched the earth 18 their classrooms. Thanks to Wasana's 19 action and careful observation, 20 was hurt in the incident. | ||||
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