If a function is given

and it asks if a point is on the graph.
How am I supposed to solve this?

Like for example: f(x)= (2x)/(x-2)

point: (1/2,-2/3)

calculate f(1/2)=(2*(1/2))/((1/2)-2) and see if it matches the value of "y" equal to -2/3.

If f(1/2) evaluates to -2/3, then P(1/2,-2/3) is on the graph.