Right-click on the slider above named 'a' and choose Animation On.
What features of the graph change, and what features remain the same?
In the AlgebraView window at left, notice how the equation f(x)  changes.
Explain that change in terms of the slider value.

a = 1 (slider from -4 to 4, step 0.5)
f(x) = (x - 3.0) / (x - a)
b: x = a