One way to solve the function is to choose any 2 points on either of the 2 graphs. Then compare the 2 points and see what difference needed to have occurred to give the point on the f(x) graph.
Look if the change is made to the x and or the y coordinates. Knowing this, either place the change in brackets for the x values or simply outside for the y values.
The function is most likely F(x) = X^2 + 2.
Way