Mathematics for IGCSE & O level - Coordinate Geometry (Section 4 - No. 19)
What is the equation of a line that is perpendicular to y = x + 3 and passes through the point (1, 2)?
y = -x + 3
y = -x + 2
y = x + 1
y = -x + 1
คำอธิบาย
The gradient of the perpendicular line is -1. Using point-slope form y-2 = -1(x - 1) -> y = -x + 1+ 2 => y = -x + 3