Taking input as f(x) into graphing calculator

I am having trouble with slide 4 on my activity Graphs of Logarithms - Lesson 17 Day 2 • Activity Builder by Desmos

I want the students to be able to input f(x) = 5^x. The way I have it set up is so close to working. If I use y = as the initial text, it works. Later in the activity, they will be graphing f(x) and g(x) and comparing, so I don’t want to use y=notation.
I have tried using x, f. I’ve tried parsing into left and right sides. I just don’t understand it well enough to figure out how to fix it. Any help is appreciated!

Not sure if this is what you are looking for but here you go.
I prefer to parse the equation and then just use the right hand side (rhs).