Question

Calculus


help me differentiate this:

d/dx (x^3- (7/x))^-2


My answer is -2(x^3-7/x)^-3(3x^2+7x^-2)

Answer 1

that's right!

Answer 2

wolf alpha gives a different answer https://www.dropbox.com/s/xma83v325e10s8u/Screenshot%202015-12-02%2023.29.15.png?dl=0

Answer 3

I copy pasted your problem with an equals sign to your answer you wrote and Wolfram Alpha returned true! :P

http://www.wolframalpha.com/input/?i=d%2Fdx%20(x%5E3-%20(7%2Fx))%5E-2%20%3D%20-2(x%5E3-7%2Fx)%5E-3(3x%5E2%2B7x%5E-2)&t=crmtb01

Answer 4

Thank you guyssss ! :D:D

Answer 5

many many kudos !

Answer 6

oops.. I have made a typo:
\[\huge \begin{gathered}
- 2{\left( {{x^3} - \frac{7}{x}} \right)^{ - 3}}\left( {3{x^2} + \frac{7}{{{x^2}}}} \right) = \hfill \\
\hfill \\
= - 2\frac{{\frac{{3{x^4} + 7}}{{{x^2}}}}}{{{{\left( {\frac{{{x^4} - 7}}{x}} \right)}^3}}} = \hfill \\
\hfill \\
= \frac{{ - 2x\left( {3{x^4} + 7} \right)}}{{{{\left( {{x^4} - 7} \right)}^3}}} \hfill \\
\end{gathered} \]