Q: derivative for finite positive integral K I can't figure out what this question is asking for,

Compute the derivative with respect to x of the function
$$
f(x) = \log\left(\sum_{k = 1}^K \exp(k x^k)\right)\:\text{ for finite, positive, integral }K.
$$

I am assuming that I need to take the derivative of this function where:
$$
\frac{df(u)}{dx} = \frac{df}{du}\frac{du}{dx}
$$ where $u=\sum_{k = 1}^K \exp(k x^k)  f = log(u)$
And yes, it is an assignment question, in my Machine Learning class.

A: With your definition of $u$, what you are asked to find is
$$
\frac{df}{dx}=\frac{d}{dx}\log u=\frac{d\log u}{du}\,\frac{du}{dx}=\frac{1}{u}\,\,u'.
$$
I'm sure you can find $u'$.
