f(x)=(x^5-4/x)^-4
f'(x)=
gave me -4(5x^4-4)/(x^5-4/x)^5 , but its wrong
That does work, but you can also do it by rewriting it first as then using the power rule, which gives you , then changing it back to a fraction to get .
By the way, in general, you'll probably want to just commit to memory that the derivative of is since it seems to come up often enough that it will be a time saver to just learn it.