WAEC 2014 Mathematics · Question 2
If is equal to , find p
Options
- A.-x - 5
- B.-(x + 3)
- C.5x - 13
- D.5 - x
Answer: D. 5 - x
Explanation written with AI and checked against the answer key
Analyze the question: We need to combine two fractions into a single fraction over the common denominator (x − 3)(x − 2) and read off the numerator p.
Concept: To subtract fractions, use the common denominator. Multiply each numerator by the factor missing from its denominator.
Solution:
2/(x − 3) − 3/(x − 2)
= [2(x − 2) − 3(x − 3)] / [(x − 3)(x − 2)]
Expand the numerator:
- 2(x − 2) = 2x − 4
- 3(x − 3) = 3x − 9
Numerator = (2x − 4) − (3x − 9) = 2x − 4 − 3x + 9 = −x + 5 = 5 − x
So p = 5 − x.
Check with a value: Let x = 4.
- Left side: 2/1 − 3/2 = 2 − 1.5 = 0.5
- Right side: p/(1·2) with p = 5 − 4 = 1 gives 1/2 = 0.5 ✓
Answer: D (5 − x)
Tip: The most common mistake is forgetting to distribute the minus sign over the second bracket: −3(x − 3) = −3x + 9, not −3x − 9. Always put brackets around the second numerator before expanding.
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