Inequality as Distance

The locus of points P on the number line such that the distance between P and the point 2 is between 1 and 7 inclusive, is:

  1. P ≤ 1 or P ≥ 3
  2. 1 ≤ P ≤ 3
  3. -5 ≤ P ≤ 9
  4. -5 ≤ P ≤ 1 or 3 ≤ P ≤ 9
  5. -6 ≤ P ≤ 1 or 3 ≤ P ≤ 10


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Draw it!

So (d).

Or translate it: 1 ≤ |P – 2| ≤ 7
We have two cases: P – 2 > 0 and P – 2 < 0 Case I: P – 2 > 0 and 1 ≤ P – 2 ≤ 7 → P > 2 and 3 ≤ P ≤ 9

Case II: P – 2 < 0 (so 2 - P > 0) and 1 ≤ 2 – P ≤ 7 → P < 2 and -1 ≤ -P ≤ 5
P < 2 and 1 ≥ P ≥ -5

So the answer is (d).

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