# Math Help - national exams Mathematics C problem

1. ## national exams Mathematics C problem

Hi, I've got this assignment: "Decide the smallest value to the function $f(x)= x^4/4 + x^3$. I know how to differentiate but I got a bit unsecure when the divided by four got there.

2. ## Re: national exams Mathematics C problem

To differentiate $a\cdot g(x)$ where $a$ is a constant ( $a = 1/4$ in this case), differentiate $g(x)$ and multiply the result by $a$. So, what do you get when you differentiate $f(x)$ and equate it to 0?

3. ## Re: national exams Mathematics C problem

Originally Posted by theraz
Hi, I've got this assignment: "Decide the smallest value to the function $f(x)= x^4/4 + x^3$. I know how to differentiate but I got a bit unsecure when the divided by four got there.
Check if you need brackets, as posted this is rather trivial, would be more interesting (well slightly) if you were asked for the derivative of :

$f(x)=\frac{x^4}{4+x^3}$

CB

4. ## Re: national exams Mathematics C problem

Originally Posted by CaptainBlack
Check if you need brackets, as posted this is rather trivial, would be more interesting (well slightly) if you were asked for the derivative of :

$f(x)=\frac{x^4}{4+x^3}$

CB
it looks like this, I'm sorry I didn't know how to write it properly.

$f(x)=\frac{x^4}{4}+x^3$