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.