I assume f(1/2x) means f((1/2)x) = f(x/2) and not f(1/(2x)).

Why do you have lines?? You don't have to be a line to have an x-intercept and a y-intercept!

x-intercept has coordinates (a, 0).

y-intercept has coordinates (0, b).

If f(x) ---> f(x/2) then the genreal point (A, B) on y = f(x) transforms to (2A, B).

Therefore .....