Question

Difficulty: MediumInequalities and Absolute Value Equations

If nn is an integer such that ∣3−2n∣≤9|3 - 2n| \le 9 and ∣n−1∣≥2|n - 1| \ge 2, what is the sum of all possible values of nn?

Answer: 12

Answer

The sum of all possible integer values of nn is 12.
Solving ∣3−2n∣≤9|3 - 2n| \le 9 gives −3≤n≤6-3 \le n \le 6. Solving ∣n−1∣≥2|n - 1| \ge 2 restricts nn to n≤−1n \le -1 or n≥3n \ge 3. Taking the intersection yields the integer set {−3,−2,−1,3,4,5,6}\{-3, -2, -1, 3, 4, 5, 6\}, whose sum equals 12.

Step-by-Step Solution

1
Unpack and solve ∣3−2n∣≤9|3 - 2n| \le 9
−3≤n≤6-3 \le n \le 6
Removing absolute value yields −9≤3−2n≤9-9 \le 3 - 2n \le 9. Dividing by −2-2 requires reversing the inequality direction.
2
Unpack and solve ∣n−1∣≥2|n - 1| \ge 2
n≤−1n \le -1 or n≥3n \ge 3
An absolute value greater than or equal to 2 implies distance from 1 is at least 2 units in either direction.
3
Determine the intersection set of integers
{−3,−2,−1,3,4,5,6}\{-3, -2, -1, 3, 4, 5, 6\}
Filters out integers 0, 1, and 2 from the continuous range [−3,6][-3, 6].
4
Calculate the sum of the valid integers
12
Summing (−3)+(−2)+(−1)+3+4+5+6=12(-3) + (-2) + (-1) + 3 + 4 + 5 + 6 = 12.

Key Concept

Combining system of absolute value inequalities and handling inequality sign flips when dividing by negative quantities.
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