# Find max/min within what we've been taught?

Hi,

I have the function $$0.1x^3 - 3x$$ and I would like to find its local maxima and minima within the domain of [-10,10]. The problem is I don't think we've been taught a way yet; I'm currently in Calculus I and just before derivatives. Is there a way within my current knowledge to find the fraction representing the max and min of this function within the above domain?

## Answers and Replies

vsage
I would think that the local max and min could be approximated by taking the midpoint x value between roots. Edit: Have you been taught limit notation yet?

dextercioby
Science Advisor
Homework Helper
Can't u use a computer & graph it...?

Daniel.

Yeah we've been taught limit notation. And we can probably just give the value 3.1622... but I'm trying to be as thorough as possible.

We have roots
$$\sqrt{1.2}/1.2 and 0$$
The midpoint isn't the max/min cause the function isn't linear (i think thats why).

dextercioby
Science Advisor
Homework Helper
Unfortunately u can find the exact (x,y) values or the extrem through calculus.Approximate values can be achived by plotting...It has 3 roots,BTW

Daniel.

vsage
If you know limit notation I think you can cheat and use the definition of a derivative.