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

f'(x)=

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

Printable View

- Apr 19th 2010, 06:13 PMwannousderivative
f(x)=(x^5-4/x)^-4

f'(x)=

gave me -4(5x^4-4)/(x^5-4/x)^5 , but its wrong - Apr 19th 2010, 06:16 PMharish21
- Apr 19th 2010, 06:29 PMwannous
only the -4 is divided by x

- Apr 19th 2010, 06:35 PMdrumist
So it is:

It looks like your derivative of was wrong.

- Apr 19th 2010, 06:41 PMwannous
aww so i needed to use quotient rule on the 4/x

- Apr 19th 2010, 06:49 PMdrumist
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.