第17题: [单项选择]y=x3-3x2的拐点为______。 A. (1,-2) B. (0,0) C. (-1,-4) D. (2,-4) 参考答案:A 答案解析:y′=3x2-6x,y″=6x-6,令y″=0,得x=1。故在x=1的左右出现y″异号,所以拐点为(1,-2),选A。 拐点的必要条件是在该点的二阶导数为零。
第28题: [单项选择]The aim of the agreement is to ______. A. encourage trade in the region B. crack down on drug smuggling C. save the declining fishing industry D. strengthen cross-boarder police presence 参考答案:A 答案解析:[听力原文]21-23
The Canadian police say that the new North American Free Trade Agreement which is to
第29题: [单项选择]频淬火铸铁导轨面的淬火深度可达()MM A. 0.5~0.8 B. 0.8~1 C. 1~1.5 D. 1.5~2 参考答案:D