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WAEC Further Mathematics 2007 Question 30

Question 30

Coordinate Geometry

The equation of a circle is given by x2 + y2 − 4x + 2y − 3 = 0. Find the radius and the coordinates of its centre.

  1. A.3, (−1, 2)
  2. B.2√2, (2, −1)
  3. C.2√2, (2, 1)
  4. D.9, (2, −1)
Show the answer and explanation

Answer: B (2√2, (2, −1))

Explanation

Complete the squares: (x − 2)² + (y + 1)² = 3 + 4 + 1 = 8. Centre (2, −1), radius √8 = 2√2.