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WAEC Further Mathematics 2006 Question 26

Question 26

Differentiation

Find the coordinates of the point on the curve y = x2 + 4x − 2, where the gradient is zero.

  1. A.(−2, 10)
  2. B.(−2, 2)
  3. C.(−2, −2)
  4. D.(−2, −6)
Show the answer and explanation

Answer: D ((−2, −6))

Explanation

dy/dx = 2x + 4 = 0 gives x = −2. Then y = 4 − 8 − 2 = −6, so the point is (−2, −6).