JAMB 2011 Mathematics · Question 15
Solve the inequality -6(x + 3) 4(x - 2)
Options
- A.x 2
- B.x -1
- C.x -2
- D.x -1
Answer: B. x -1
Explanation written with AI and checked against the answer key
Analysis
To solve the inequality , we need to expand the brackets, collect like terms, and isolate the variable . A crucial rule to remember is that when you divide or multiply an inequality by a negative number, the inequality sign must be reversed.
Concept
- Expansion: Use the distributive property to remove the brackets.
- Grouping: Move all terms containing to one side and constant terms to the other.
- Division: Divide by the coefficient of . If the coefficient is negative, flip the inequality sign ( becomes ).
Step-by-Step Solution
Step 1: Expand the brackets
Step 2: Collect like terms Move to the left side and to the right side:
Step 3: Simplify both sides
Step 4: Solve for Divide both sides by . Because we are dividing by a negative number, the inequality sign changes to :
Conclusion
Comparing our result () with the given options, it matches option B.
Exam Tip: Always double-check your sign when dividing by a negative number! Many students lose marks here by forgetting to flip the inequality sign. If you are ever unsure, pick a number that satisfies your final answer (e.g., ) and plug it back into the original equation to see if it holds true.
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