Mathematics for IGCSE & O level - Coordinate Geometry (Section 2 - No. 20)
Which of the following equations is perpendicular to the line y = (2/5)x - 3?
y = (2/5)x + 1
y = -(5/2)x + 1
y = (5/2)x + 1
y = -(2/5)x + 1
คำอธิบาย
The gradient of a perpendicular line must be the negative reciprocal of 2/5, which is -5/2.