Find y max

Here is how I'm approaching this ...

With 3 being a critical point

So the critical point is a maximum. It's a parabola opening downward from 3?

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- February 22nd 2008, 07:56 AMXIII13ThirteenFinding maximum

Find y max

Here is how I'm approaching this ...

With 3 being a critical point

So the critical point is a maximum. It's a parabola opening downward from 3? - February 22nd 2008, 08:52 AMwingless
We have

But

??

??

These are wrong.

But I see what you were trying to do.

It should be,

I know, the root doesn't change by multiplication or division, but is not correct. - February 22nd 2008, 09:24 AMXIII13Thirteen
Thank you for clarifying. I'm prone to making mistakes and that is why I like to double check. Looking at the equation is still seems 3 is our critical point, but the differences in our y' will become ...

Which should still give us 3 as our maximum with a downward opening parabola. I appreciate the help as this mistake could have cost me in other equations - February 22nd 2008, 09:45 AMgalactus
Are you just trying to find the max of ?.

Did you just differentiate?.

3-x=0, x=3

That gives y=9/2 as the max value for y.

If I am misunderstanding, I apologize. - February 22nd 2008, 09:54 AMwingless
- February 22nd 2008, 09:59 AMgalactus
You can also find this without calc by using .

Which gives the x-coordinate for the vertex of a parabola.

In your case, a=-1/2 and b=3

- February 22nd 2008, 10:09 AMXIII13Thirteen
Your correct.

The equation wanted "y max," not "x max" so technically it is is correct. I'm doing these equations with a multiple choice solution set and he has

a.)4

b.)3

c.)-1

d.)none of these

I originally picked b because I was thinking of in terms of x, but in the context of "find y max" . Evil questions. Thanks for catching that