a(1,1) and b(3, 1) Find the perpendicular bisector
find the slope M = (Ya - Yb)/(Xa - Xb)
M = 1 - 1/1 - 3 = 0 This line goes right to left parallel to the x-axis at y = 1
The midpoint is (1-3/2, 1-1/2)
(-1,0)
The perpendicular bisector is a line that goes up and down along x = -1