Gradient in the UK = slope in the U.S.
The gradients of perpendicular lines are negative reciprocals.
That means the gradients of perpendicular lines are two numbers whose product is -1.
If you know the gradient of a line, to find the gradient of a perpendicular to that line, write the gradient as a fraction. Flip the fraction. Change the sign.
a) gradient = 4 = 4/1
flip the fraction: 1/4
change the sign: -1/4
The gradient of the perpendicular is -1/4
b) gradient = -3 = -3/1
flip the fraction: -1/3
change the sign: 1/3
The gradient of the perpendicular is 1/3
c) gradient = 2/3 (already a fraction)
flip the fraction: 3/2
change the sign: -3/2
The gradient of the a perpendicular is -3/2
