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JAMB Mathematics 2001 Question 30

Question 30

Coordinate Geometry

Find the value of p if the line joining (p, 4) and (6, −2) is perpendicular to the line joining (2, p) and (−1, 3).

  1. A.0
  2. B.3
  3. C.4
  4. D.6
Show the answer and explanation

Answer: C (4)

Explanation

The gradients are −6/(6 − p) and (p − 3)/3. Their product must be −1: 6(p − 3) = 3(6 − p), so 9p = 36 and p = 4.