2018年云南中考数学试题解析
一、选择题（共8小题，每小题3分，满分24分）
1．5的相反数是（ ）
| A． |
| B． | ﹣5 | C． |
| D． | 5 |
考点： | 相反数。1052629 |
分析： | 根据相反数的定义，即只有符号不同的两个数互为相反数，进行求解． |
解答： | 解：5的相反数是﹣5． 故选B． |
点评： | 此题考查了相反数的概念．求一个数的相反数，只需在它的前面加“﹣”号． |
2．如图是由6个形同的小正方体搭成的一个几何体，则它的俯视图是（ ）
![](https://wkrtcs.bdimg.com/rtcs/image?w=102&md5sum=f5a5507946edc60d840fa28028c959df&sign=2f28f92390&rtcs_flag=1&rtcs_ver=3&l=webapp&bucketNum=100&ipr={"t":"img","w":"102","h":"119","dataType":"png","c":"word/media/image4.png","imgOriW":102,"imgOriH":120})
| A． |
| B． |
| C． |
| D． |
|
考点： | 简单组合体的三视图。1052629 |
分析： | 根据俯视图是从上面看到的识图分析解答． |
解答： | 解：从上面看，是1行3列并排在一起的三个正方形． 故选A． |
点评： | 本题考查了三视图的知识，俯视图是从物体的上面看得到的视图． |
3．下列运算正确的是（ ）
| A． | x2•x3=6 | B． | 3﹣2=﹣6 | C． | （x3）2=x5 | D． | 40=1 |
考点： | 负整数指数幂；同底数幂的乘法；幂的乘方与积的乘方；零指数幂。1052629 |
分析： | 利用同底数幂、负指数、零指数以及幂的乘方的性质求解即可求得答案，注意排除法在解选择题中的应用． |
解答： | 解：A、x2•x3=x6，故本选项错误； B、3﹣2= C、（x3）2=x6，故本选项错误； D、40=1，故本选项正确． 故选D． |
点评： | 此题考查了同底数幂、负指数、零指数以及幂的乘方的性质．注意掌握指数的变化是解此题的关键． |
4．不等式组![](https://wkrtcs.bdimg.com/rtcs/image?w=84&md5sum=f5a5507946edc60d840fa28028c959df&sign=2f28f92390&rtcs_flag=1&rtcs_ver=3&l=webapp&bucketNum=100&ipr={"t":"img","w":"84","h":"43","dataType":"png","c":"word/media/image11.png","imgOriW":84,"imgOriH":43})
的解集是（ ）
| A． | x＜1 | B． | x＞﹣4 | C． | ﹣4＜x＜1 | D． | x＞1 |
考点： | 解一元一次不等式组。1052629 |
分析： | 先求出不等式组中每一个不等式的解集，再求出它们的公共部分，即可得到不等式组 |
解答： | 解： 由①得﹣x＞﹣1，即x＜1； 由②得x＞﹣4； 由以上可得﹣4＜x＜1． 故选C． |
点评： | 主要考查了一元一次不等式解集的求法，其简便求法就是用口诀求解，求不等式组解集的口诀：同大取大，同小取小，大小小大中间找，大大小小找不到（无解）． |
5．如图，在△ABC中，∠B=67°，∠C=33°，AD是△ABC的角平分线，则∠CAD的度数为（ ）
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