Two lines of gradient m1 and m2 are perpendicular if m1m2 = -1
Find the gradient of a line perpendicular to the line with equation y = 4x - 3
The gradient, m1, of y = 4x - 3 is the coefficient of x, so
m1 = 4
m1m2 = -1, where m2 is the gradient of a line perpendicular to the given line.
4m2 = -1
m2 = -¼