For this problem, make a right triangle between these two points. To solve for distance, use the Pythagorean formula. We know that one side is 8, and the other side is 9, so square 8 and 9 to get 64 plus 81. When you add these together, you get the square root of 145. You cannot further simplify the square root of 145, so that is the distance between the pair of points.
For any two points there is exactly one line segment connecting them. The distance between two points is the length of the line segment connecting them. Note that the distance between two points is always positive. Segments that have equal length are called congruent segments.
