Mathematics for IGCSE & O level - Coordinate Geometry (Section 1 - No. 18)
If two lines are perpendicular, and one has the equation y = (1/3)x + 2, what is a possible equation for the other line?
y = (1/3)x + 5
y = 3x - 1
y = -3x + 4
y = -1/3x + 2
คำอธิบาย
The gradient must be the negative reciprocal of 1/3, which is -3. y = -3x +4 satisfies.