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WAEC Further Mathematics 2012 Question 13

Question 13

Coordinate Geometry

If the mid-point of the line joining (1 − k, −4) and (2, k + 1) is (−k, k), find the value of k.

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

Answer: B (−3)

Explanation

x-coordinate: (1 − k + 2)/2 = −k gives 3 − k = −2k, so k = −3. Check y: (−4 + k + 1)/2 = (−3 − 3)/2 = −3 = k.