Freely drag the points A and B to change the slope and equation of the line L. Pay attention to the change in y and change in x from A to B. [br][br]You may use this figure to discuss with students about the concept and calculation of slope. You may also discuss methods of finding an equation or alternative ways to write it. Consider how and when to show or hide individual objects or information (including the grid and axes) during the discussion.

In this construction, as shown in the silent video below, the symbols x(A) and y(A) mean the x- and y- coordinates of point A. Point C is defined in terms of the coordinates of A and B. The vectors are drawn to indicate the horizontal and vertical changes. The captions of the vectors can be changed to %x and %y by editing the object property. For details about setting captions, see https://wiki.geogebra.org/en/Labels_and_Captions