1962 AMC 12 第 33 题

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33.

满足不等式 2x152\le|x-1|\le5xx 值集合为:

The set of xx-values satisfying the inequality 2x152\le|x-1|\le5 is:

4x1-4\le x\le-13x63\le x\le6

4x1-4\le x\le-1 or 3x63\le x\le6

3x63\le x\le66x3-6\le x\le-3

3x63\le x\le6 or 6x3-6\le x\le-3

x1x\le-1x3x\ge3

x1x\le-1 or x3x\ge3

1x3-1\le x\le3

4x6-4\le x\le6

答案:A
知识点:绝对值不等式
难度评级:1180
小提示:

将该不等式理解为到 11 的距离介于 2255 之间

Interpret the inequality as distances from 11 between 22 and 55

大提示:

分别解 2x152\le x-1\le55x12-5\le x-1\le-2

Solve 2x152\le x-1\le5 and 5x12-5\le x-1\le-2

解答:

x10x-1\ge0 时,界限给出 3x63\le x\le6。当 x10x-1\le0 时,给出 4x1-4\le x\le-1。解集是这两个区间的并集。

所以正确答案是 A

For x10,x-1\ge0, the bounds give 3x6.3\le x\le6. For x10,x-1\le0, they give 4x1.-4\le x\le-1. The solution is the union of these two intervals.

Thus, the correct answer is A.

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