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I have the function $f(x,y)=(x^3)*y - (y^3)*x$.

I have to find $[(df/dx) +(df/dy)]/[(df/dx) *(df/dy)]$.

So,what I dont get is how to find $df/dx$ or $df/dy$..

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put on hold as off-topic by Jonas, Edward Jiang, Luiz Cordeiro, choco_addicted, Ramiro 2 days ago

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Jonas, Edward Jiang, Luiz Cordeiro, choco_addicted, Ramiro
If this question can be reworded to fit the rules in the help center, please edit the question.

The function $f$ depends on two variables $x$ and $y$ and when you want to derive $f$ relative to $x$ you must treat $y$ as a constant so you have: $$\frac{\partial}{\partial x}f(x,y)=3yx^2-y^3$$ Now I think you can calculate $\frac{\partial}{\partial y}f(x,y)$ by the same method.

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