NECO 2008 Mathematics · Question 17
P = {x:(x - 2)(x + 3) (x - 4)(x + 5) = 0}. The elements in P are
Options
- A.-5,-2, 3, 4
- B.-5, -3, 2, 4
- C.-5, -3, -2,4
- D.-4, -3, -2, 5
- E.2, 3, 4, 5
Answer: B. -5, -3, 2, 4
Explanation written with AI and checked against the answer key
Analyze the question: P is the set of all values of x that make the product equal to zero. We need to find every such value.
Concept: The Zero Product Property says that if a product of factors equals zero, then at least one factor must equal zero. So we set each factor equal to zero and solve.
Solution:
(x − 2)(x + 3)(x − 4)(x + 5) = 0
- x − 2 = 0 → x = 2
- x + 3 = 0 → x = −3
- x − 4 = 0 → x = 4
- x + 5 = 0 → x = −5
So P = {−5, −3, 2, 4}.
Check against the options:
- A (−5, −2, 3, 4): has −2 and 3, which are wrong signs
- B (−5, −3, 2, 4): matches exactly
- C (−5, −3, −2, 4): −2 is wrong
- D (−4, −3, −2, 5): wrong
- E (2, 3, 4, 5): all signs are wrong
Tip: For a factor like (x − a), the root is +a. For (x + a), the root is −a. The sign flips, so a quick way to avoid mistakes is to ask, "What value of x makes this bracket zero?"
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