The Wolfram Language applies the chain rule for differentiation, and leaves the result in terms of f'.
When a function has more than one argument, superscripts are used to indicate how many times each argument is being differentiated.
This represents . The Wolfram Language assumes that the order in which derivatives are taken with respect to different variables is irrelevant.
|f '[x]||first derivative of a function of one variable|
|f(n)[x]||n derivative of a function of one variable|
|Null||derivative of a function of several variables, ni times with respect to variable i|