Question

explain how to find domain of a rational function from it's graph

Answer 1

Your graph would look like a curve of sorts, right?

Answer 2

Its domain is simply all the x-values on the x-axis that have a correspond to a point somewhere on that curve.

Answer 3

Well tbh you're limited to the information represented by the graph, which is obviously finite. For end behavior, you really have to know what kind of conventions your teacher uses.