JAMB 2010 Mathematics · Question 38
Solve the inequalities -6 4 - 2x < 5 - x
Options
- A.-1 < x < 5
- B.-1 < x 5
- C.-1 x 6
- D.-1 x < 6
Answer: B. -1 < x 5
Explanation written with AI and checked against the answer key
Analyze the question: This is a compound inequality: -6 ≤ 4 - 2x < 5 - x. We split it into two inequalities, solve each, and then find where both are true.
Concept: When you multiply or divide an inequality by a negative number, the inequality sign flips.
Solution:
Part 1: -6 ≤ 4 - 2x
- Subtract 4 from both sides: -10 ≤ -2x
- Divide by -2 (flip the sign): 5 ≥ x, so x ≤ 5
Part 2: 4 - 2x < 5 - x
- Add 2x to both sides: 4 < 5 + x
- Subtract 5: -1 < x, so x > -1
Combine: x > -1 and x ≤ 5, so
-1 < x ≤ 5
Check:
- x = 5: 4 - 10 = -6, and -6 ≤ -6 is true. Also -6 < 0 is true. So x = 5 is included.
- x = -1: 4 + 2 = 6 and 5 + 1 = 6, so 6 < 6 is false. So x = -1 is excluded.
- x = 0: -6 ≤ 4 < 5 is true.
Tip: Treat a compound inequality as two separate inequalities. Remember to flip the sign when dividing by a negative. Then test the endpoints to decide whether each is included (≤) or excluded (<).
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