Everytime I try derivative or anything like that, I get 1 or 2 errors depending on what I do..

Situation 1: If I tell nspire to solve for x

Error: Missing )

Situation 2: If i dont tell nspire to solve for x

Define variable

This counts for anything with variable. It seems to me that it is some kind of option that i have to disable in order to allow me to use x y z or whatever as variables for f(x) etc.

I have my exam tomorrow, so I would appreciate any help at all!