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WAEC Further Mathematics 2014 Question 3

Question 3

Coordinate Geometry

Given that the lines 3x + 4y + 6 = 0 and 4x − by + 3 = 0 are perpendicular, find the value of b.

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

Answer: B (3)

Explanation

Gradients are −3/4 and 4/b. Perpendicular: (−3/4)(4/b) = −1, so b = 3.