testing header
Math Goodies is a free math help portal for students, teachers, and parents.
Free Math
Newsletter
 
 
Interactive Math Goodies Software

Buy Math Goodies Software
testing left nav
Math Goodies on facebook

Math Goodies Blog
Math Forums @ Math Goodies
Math Forums @ Math Goodies
Home | Profile | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Homework Help Forums
 Pre-Calculus and Calculus
 Finding critical points
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

Kevitzinn
Average Member

USA
14 Posts

Posted - 10/19/2007 :  13:53:53  Show Profile  Reply with Quote
So I have, y = x(2-x) and I find the derivative is

y' = (x)/(3(2-x)^(2/3)) + (2-x)

Is there some easy way to find the critical points of that? Thank you very much for your time.
Go to Top of Page

skeeter
Advanced Member

USA
5634 Posts

Posted - 10/19/2007 :  14:47:03  Show Profile  Reply with Quote
y = x(2 - x)1/3

y' = x*(1/3)(2 - x)-2/3*(-1) + (2 - x)1/3

y' = (2 - x)-2/3[-(x/3) + (2 - x)]

y' = (2 - x)-2/3[2 - (4x/3)]

y' = [2 - (4x/3)]/(2 - x)2/3

you should be able to almost "see" the critical values now.

Go to Top of Page

Kevitzinn
Average Member

USA
14 Posts

Posted - 10/19/2007 :  16:26:24  Show Profile  Reply with Quote
I see you have the right answer and I appreciate your time very much, but I have just one more question.

You said:

y' = (2 - x)-2/3[-(x/3) + (2 - x)]

What I'm confused about is, how did you do that? If -x/3 is to the first power and and (2-x) is to the (1/3) power, how can you pull it out like that? Thanks.
Go to Top of Page

Kevitzinn
Average Member

USA
14 Posts

Posted - 10/21/2007 :  23:53:39  Show Profile  Reply with Quote
Ohhhh, that's amazing! Thanks for the help, I would have never thought it could have been pulled out like that! Again, thanks a lot for the help, this site is the best.
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Math Forums @ Math Goodies © 2000-2004 Snitz Communications Go To Top Of Page
This page was generated in 0.05 seconds. Snitz Forums 2000
testing footer
About Us | Contact Us | Advertise with Us | Facebook | Blog | Recommend This Page




Copyright © 1998-2015 Mrs. Glosser's Math Goodies. All Rights Reserved.

A Hotchalk/Glam Partner Site - Last Modified 25 Jan 2015