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I'm not sure how to find the solution set for a compound absolute value with different left and right values. Here is an example:

A = { 2 ≤ |x| < 4 : x ε integers }

My thinking is to create two inequality statements. Such as:

|x| ≥ 2 and |x| < 4

Solving for each:

-2 ≥ x ≥ 2 and -4 < x < 4

Since |x| cannot be a negative number, would my solution set be:

{ 0, 1, 2, 3 } ?

Thanks in advance

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  • $\begingroup$ Interpret it as a distance statement, $|x|=|x-0|$. All real x which lie a distance of at least 2 but less than 4 from 0. So $(-4,-2] \cup [2, 4)$. Picking just the integers from this list give $\{-3,-2,2,3\}$ $\endgroup$
    – David P
    Sep 16, 2014 at 19:15

2 Answers 2

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We want $2\le |x|<4$. That means $|x|=2$ or $|x|=3$, which means $x=-2,2,3,-3$.

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Note that $|x|\ge 2$ is not the same as $-2\ge x\ge 2$ (there is no such $x$) and that $$|x|\ge 2\iff x\le -2\ \ \text{or}\ \ x\ge 2.$$

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