JAMB 2011 Mathematics · Question 12
Evaluate (3 - 2x)dx
Options
- A.33m
- B.5
- C.2
- D.6
Answer: C. 2
Explanation written with AI and checked against the answer key
Analyze the question: We need the definite integral of (3 − 2x) from x = 0 to x = 1.
Concept: For a definite integral, find the antiderivative, then compute F(upper) − F(lower).
Power rule: ∫xⁿ dx = xⁿ⁺¹/(n+1) + C
Solution:
∫₀¹ (3 − 2x) dx = [3x − x²]₀¹
At x = 1: 3(1) − (1)² = 3 − 1 = 2
At x = 0: 3(0) − 0² = 0
Result: 2 − 0 = 2
Check against the options:
- A. "33m" is clearly a typing error and not a valid answer.
- B. 5: no.
- C. 2: matches our working.
- D. 6: no.
The correct answer is **C.
Tip: For a linear integrand like this, you can double-check using geometry. The function goes from 3 at x = 0 to 1 at x = 1, so the area is a trapezoid with average height (3 + 1)/2 = 2 and width 1, giving 2 × 1 = 2. Also, remember to subtract the lower-limit value, even when it is 0, because in other questions it often will not be.
AI can make mistakes. Report anything that looks wrong.
Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.
