中考数学复习高分冲刺

解：

5x 1 2x 5，①

x 4 3x 1②由①得x 2， ················································································································· 2分

5

由②得，x ············································································································· 4分

2

························································································ 6分 原不等式组的解集为x 2 ·

20．本小题满分8分.

解：（Ⅰ）这个反比例函数图象的另一支在第三象限. ··················································· 1分 因为这个反比例函数的图象分布在第一、第三象限， 所以m 5 0，解得m 5. ·························································································· 3分 （Ⅱ）如图，由第一象限内的点A在正比例函数y 2x的图象上，

设点A的坐标为 x0，2x0 x0 0 ，则点B的坐标为 x0，0 ，

1 S△OAB 4， x0·2x0 4，解得x0 2（负值舍去）.

2

········································································

4 . · 点A的坐标为 2，又 点A在反比例函数y

m 5

的图象上， x

4

m 5

，即m 5 8. 2

8. ···················································································· 8分 x

反比例函数的解析式为y

21．本小题满分8分.

解（Ⅰ）法一：根据题意，可以画出如下的树形图：

3 2 第一个球 1

2 第二个球 3 3

从树形图可以看出，摸出两球出现的所有可能结果共有6种； 法二：根据题意，可以列出下表： 第二个球 （1，3） （2，3）

3 （1，2） （3，2）

2

（2，1） （3，1） 1

1 2 3 第一个球

从上表中可以看出，摸出两球出现的所有可能结果共有6种. ······································ 4分 （Ⅱ）设两个球号码之和等于5为事件A.

摸出的两个球号码之和等于5的结果有2种，它们是： 2，，，3 32 .

P A

21 . ············································································································· 8分 63

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