JAMB 2021 Mathematics · Question 19
List all integers satisfying the inequality in -2 < 2x-6 < 4
Options
- A.2,3,4 and 5
- B.2,3
- C.2,5
- D.3,4
Answer: D. 3,4
Explanation written with AI and checked against the answer key
Analyze the question: We need all integers x for which 2x − 6 lies strictly between −2 and 4.
Concept: A compound inequality can be solved by doing the same operation on all three parts. The inequality signs are strict (< not ≤), so the end values are not included.
Solution:
−2 < 2x − 6 < 4
Add 6 to all parts: 4 < 2x < 10
Divide all parts by 2: 2 < x < 5
The integers strictly between 2 and 5 are 3 and 4.
Check:
- x = 3: 2(3) − 6 = 0, and −2 < 0 < 4 ✓
- x = 4: 2(4) − 6 = 2, and −2 < 2 < 4 ✓
- x = 2: 2(2) − 6 = −2, and −2 < −2 is false ✗
- x = 5: 2(5) − 6 = 4, and 4 < 4 is false ✗
Answer: D (3, 4)
Tip: With strict inequalities (< or >), always drop the boundary values. Testing the endpoints, as in the check above, quickly eliminates options like A, B and C.
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