Given:
The vertices of a triangle are D(1,5), O(7,-1) and G(3,-1).
To find:
The perpendicular bisector of line segment DO.
Solution:
Midpoint formula:

The midpoint of DO is:



Therefore, the midpoint of DO is (4,2).
Slope formula:

Slope of DO is:



Therefore, the slope of DO is -1.
We know that the product of slopes of two perpendicular line is -1.



The slope of perpendicular bisector is 1 and it passes through the point (4,2). So, the equation of the perpendicular bisector of DO is:




Therefore, the equation of the perpendicular bisector of DO is
.