Hi! I'll start you off on this question as I dont have time to type out a full answer, but please call out if you need more help!
For the first question, essentially it has given you an equation in terms of cosh(x)
It is also telling you the equivalent of cosh(x), which is given to you in the exponential form.
As this question is asking you to write cosh(x) in terms of the exponential form, you essentially need to sub in (e^x + e^-2)/2 wherever you see cosh(x) in the original equation. (similar to the way you'd figure out a composite function....)
So this is your first equation: 4(3-cosh(x/5))
But you know that cosh(x) also equals (e^x + e^-2)/2.
So if you sub the second equation into the first, you essentially write 4(3-(e^x/5+x^-x/5)/2)
(sorry if this doesnt make sense, I don't yet know how to write maths eqs into this!
Then if this is a TA question you can use CAS to draw the graph and find the derivative, but you could find the derivative by hand by using the quotient rule or something similar.
I really hope this made sense! I'm not very good at explaining things
Let me know if anything needs clarification, and I'll try draw up a better solution.