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JAMB Mathematics 2000 Question 40

Question 40

Differentiation

The expression ax2 + bx + c equals 5 at x = 1, if its derivative is 2x + 1, what are the values of a, b, c, respectively?

  1. A.1, 3, 1
  2. B.1, 2, 1
  3. C.2, 1, 1
  4. D.1, 1, 3
Show the answer and explanation

Answer: D (1, 1, 3)

Explanation

The derivative 2ax + b equals 2x + 1, so a = 1 and b = 1. At x = 1, a + b + c = 5, so c = 3.