题目

化简：(2a+b)(b-2a)-(a-3b)2. 答案：【答案】-5a2+6ab-8b2.【解析】原式第一项利用平方差公式计算，第二项利用完全平方公式展开，去括号合并即可得到结果．原式=b2-4a2-a2+6ab-9b2=-5a2+6ab-8b2. Look! This is our school．It is very nice．Many trees and flowers are in our school garden．Our school is small．There are fifteen classes in our school．There are fifty students in every class．We have forty teachers and one headmaster（校长）．The headmaster is Li Ming．In class，we listen to（听） our teachers．We study hard（努力学习）．After class， we often play basketball or volleyball．Our school life is very nice．We like our school，our headmaster，our teachers and our class．(1) Our school is ______． A. not small　　 B. big　　 C. too big　　 D. small [　　] (2) We have ______ teachers and ______ headmaster． A. fifty; one　　 B. fourteen; one C. forty; a　　 D. fifty-four; a [　　] (3) There are ______ students in our school． A. 600　　 B. 750　　 C. 500　　 D. 400 [　　] (4) ______ is the headmaster． A. Li Ming　　 B. Mr Liu　　 C. Liu Ming　　 D. Li Ning [　　] (5) After class，the students often ______． A. play basketball　　　　 B. play volleyball　　 C. study　　　　 D. A and B [　　]