# mixed partial derivative of a function

Find second order mixed partial derivative, $\displaystyle \frac{\partial^{2} f}{\partial y \partial x}$ of $\displaystyle \frac{x \log(y)}{ye^x}$

I tried differentiating it wrt $x$ (keeping $y$ constant) and then differentiating the result wrt $y$ (keeping $x$ as constant) but my answer is not matching.

• It is not a partial derivative. – Kenny Lau Jun 27 '16 at 13:15
• Also, what is $f$? – Kenny Lau Jun 27 '16 at 13:15
• $\dfrac{\mathrm d^2f}{\mathrm dy\ \mathrm dx}$ is really just $\dfrac{\mathrm d}{\mathrm dy}\dfrac{\mathrm df}{\mathrm dx}$. – Kenny Lau Jun 27 '16 at 13:16
• What is your answer, and what is the book's answer? – Kenny Lau Jun 27 '16 at 13:16
• Right...go ahead and show us what you did (and what the book said), and we can probably find the mistake pretty quickly. (About 20% of the time, the mistake is "the answer book is wrong and you're right." ) – John Hughes Jun 27 '16 at 13:20