Segment ab has point a located at (6, 6). if the distance from a to b is 5 units, which of the following is the coordinate for point b?

The choices are (3, 2) (2, 5) (6, 7) and (7, 5). The distance formula given two points is d = square root of [(y2−y1)^2+(x2−x1)^2]. In this case, we try every point in the choices and substitute y1 equal to 6 and x1 equal to 6 as well.  The answer is A from the choices. 
d=square root of [(6−2)^2+(6−3)2]
d=square root of [(4)^2+(3)^2] d=square root of [16+9] d=square root of [25]
d=5