Given the points A(x₁, y₁) and B(x₂, y₂). The distance between these 2 points can be calculated as below;

DistAB = (x2-x1)2+(y2-y1)2

This formula is obtained from the graph below as shown

                         Y₂

                                                                                           B(x_2, y₂)

                     y₁

                    A(x₁, y₁)

                          x₁                                                x₂

Using Pythagoras‘ theorem, (AB)²  = (x₂ – x₁)² + (y₂ – y₁)², therefore AB = (x2-x1)2+(y2-y1)2

Ex: find the distance between the points A(1, 3) and B(5, 2)

Solution:

DistAB = (x2-x1)2+(y2-y1)2 = (5-1)2+(2-3)2 = 17 units