Question 15
Coordinate GeometryA line is perpendicular to 3x − y + 11 = 0 and passes through the point (1, −5). Find its equation.
- A.3y − x − 14 = 0
- B.3x + y + 1 = 0
- C.3y + x + 1 = 0
- D.3y + x + 14 = 0
Show the answer and explanation
Answer: D (3y + x + 14 = 0)
Explanation
The given line has gradient 3, so the perpendicular has gradient −⅓. y + 5 = −⅓(x − 1) gives 3y + 15 = −x + 1, i.e. 3y + x + 14 = 0.