Two lines are perpendicular when the multiplication of their slopes is equal to minus one. In the line:
the slope is m1 = 4. Therefore, the slope, m2, of a line perpendicular to this one is:
Equation of a line in point-slope form
where m is the slope and (x1, y1) is a point on the line.
Substituting with m = -1/4 and the point (-4, 2), we get: