# Thread: Max and min value of a function over an interval

1. ## Max and min value of a function over an interval

Need some help with the following problem:

Find the maximum and minimum values of the function on the given interval.

Y=3-x/x^2+9x.....Interval [3,10]

Thank You

2. Originally Posted by elexis10
Need some help with the following problem:

Find the maximum and minimum values of the function on the given interval.

Y=3-x/x^2+9x.....Interval [3,10]

Thank You

$\displaystyle y = 3 - \frac{1}{x + 9}$.

Find the derivative.

Set this equal to 0. Solve and only keep values that are contained in [3,10].

But that's not all.

At the endpoints of the interval, you need to figure out if they are 'maximums' or 'minimums' and by that I don't mean they are stationary points.

See the function of $\displaystyle x^3$ I have attached. At the endpoints (which are indicated by the vertical black lines) we have a 'maximum' at the right hand one (near x=5) and a 'minimum' at the left hand one (near x=-5).

These are only maxs and mins on the interval.

3. ...

4. thank you for your help, i worked through it and figured it out once again thank you