Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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 $df/dy$..

share|cite|improve this 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.

share|cite|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.