passwella.
Menu

JAMB Mathematics 1995 Question 30

Question 30

Coordinate Geometry

Two perpendicular lines PQ and QR intersect at (1, −1). If the equation of PQ is x − 2y + 4 = 0, find the equation of QR.

  1. A.x − 2y + 1 = 0
  2. B.2x + y − 3 = 0
  3. C.x − 2y − 3 = 0
  4. D.2x + y − 1 = 0
Show the answer and explanation

Answer: D (2x + y − 1 = 0)

Explanation

PQ has gradient ½, so QR has gradient −2. Through (1, −1): y + 1 = −2(x − 1), i.e. 2x + y − 1 = 0.