The perpendicular bisector of a line segment must pass through its midpoint.
Midpoint = (-2, 3)
Slope of line segment = (2-4) / (-4-0) = 1/2
Slope of perpendicular bisector = -1 / (1/2) = -2
Equation of perpendicular bisector: y - 3 = -2(x + 2)
So, y = -2x - 1