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WAEC Further Mathematics 2019 Question 18

Question 18

Differentiation

Find the coordinates of the point on the curve y = 3x2 − 2x − 5 where the tangent is parallel to the line y − 5 = 8x.

  1. A.(−5/3, 0)
  2. B.(0, −5/3)
  3. C.(0, 5/3)
  4. D.(5/3, 0)
Show the answer and explanation

Answer: D ((5/3, 0))

Explanation

dy/dx = 6x − 2 = 8 gives x = 5/3; y = 25/3 − 10/3 − 5 = 0. Point (5/3, 0).