How do I plot the output of the Maximize command?

For example, here's a function that determines the value of x in the range [0,3] at which a particular fuction is maximized:

with(Optimization);

f := (x,t) -> -x^2+3*t*x-1

fmax := t -> rhs(Maximize(f(x,t),x=0..3)[2][1]);