Hello, I am having trouble trying to create a program for the Mean Value Theorem. My code looks like this:

Define LibPub meanval(a, b)=

Func

Return solve(d/dx(f1(x)) = (f1(b) - f1(a))/(b-a),x)|a<x<b

EndFunc

I then hit menu 2, 1 (to check syntax and store), then when I move over to the other side of the screen to test my code, I start by setting f1(x) = e^x + ln(x). Then, I try meanval(2, 4), and if my program works correctly, it will give me an answer of 3.163, but instead I get a jumbled mess:

x * (2.718282)^x - 23(lots of decimals) = 0.

Can someone help me and point out what is wrong? Thank you for your time.