题目

下列运算正确的是（ ） A．a3+a4=a7   B．2a3•a4=2a7 C．2（a4）3=2a7   D．a8÷a4=a2 答案：B【考点】同底数幂的除法；合并同类项；幂的乘方与积的乘方；单项式乘单项式． 【分析】根据合并同类项、同底数幂的除法、幂的乘方以及同底数幂的乘法的性质，即可求得答案． 【解答】解：A、a3与a4不能合并，故错误； B、2a3•a4=2a7，故正确； C、2（a4）3=2a6，故错误； D、a8÷a4=a4，故错误； 故阅读表达Here is something about Peter’s family. There are five people in his family. They are his father, his mother, his grandfather, his sister Kate and him. His father, Mr Brown, is a doctor.(1) _____ is thirty. Peter’s (2)_____, Mrs Brown, is a teacher. She is thirty too. Peter and his sister study in their mother’s school. Peter is in Class Two, Grade Eight. Kate is in Class Two, Grade Seven. (3)They go to school at 6:30 in the morning. Look! That old man is Peter’s grandfather. He is very old. He walks his dog every morning. Where is Kate? Look! She is under that big tree.小题1:在（1）（2）处填入合适的词或短语使句子完整。_________,  ________小题2:回答问题: Where do Kate and Peter study?_____________________________________________________________________________小题3:将（3）句译成中文。_____________________________________________________________________________ 小题4:在文中找出He takes his dog for a walk every morning.的同义句。_____________________________________________________________________________小题5:找出或写出本文的主题句。_____________________________________________________________________________