In Geometry, two points or two independent events make exactly one line.

Therefore those two things are responsible for the direction or slope of the line as well as the y-intercept.

Experience in the following in exercise #1 how the green, the red, and the yellow point change the slope and y-intercept of the line. When you finished the exercise come back here. See what the yellow point is doing.

 

Exercise #2: Match the right graphs together, and dont forget to come back here!

 

Welcome back:))

Now let's do the next step, here is exercise #3. Observe what happens to b (the y-intercept), when you move the line up and down.

In exercise #4 you can experiment how the two points of the line influence the equation of the line.

 

Click here for more information about lines, slope, and equations