Thread: derivative

f(x)=(x^5-4/x)^-4

f'(x)=

gave me -4(5x^4-4)/(x^5-4/x)^5 , but its wrong

Originally Posted by wannous

f(x)=(x^5-4/x)^-4

f'(x)=

gave me -4(5x^4-4)/(x^5-4/x)^5 , but its wrong

Is your question ?

only the -4 is divided by x

So it is:



It looks like your derivative of was wrong.

aww so i needed to use quotient rule on the 4/x

Originally Posted by wannous

aww so i needed to use quotient rule on the 4/x

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.