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

 All Forums
 Homework Help Forums
 Pre-Calculus and Calculus
 derivitives using the quotient rule
 New Topic  Topic Locked
 Printer Friendly
Author Previous Topic Topic Next Topic  

markmil2002
Average Member

USA
11 Posts

Posted - 09/17/2007 :  19:19:19  Show Profile
I'm trying to find the derivitive of f(x) = (x + 1)/(ln x)


After doing some math I got -2x/x but I don't think that is correct.
Go to Top of Page

sahsjing
Advanced Member

USA
2399 Posts

Posted - 09/17/2007 :  20:27:52  Show Profile
You should have 1/(lnx) as a factor. Try it again?
Go to Top of Page

Subhotosh Khan
Advanced Member

USA
9117 Posts

Posted - 09/18/2007 :  09:26:27  Show Profile
quote:
Originally posted by markmil2002

I'm trying to find the derivitive of f(x) = (x + 1)/(ln x)


After doing some math I got -2x/x but I don't think that is correct.




f(x) = u(x)/v(x)

df/dx = (u'*v - v'*u)/v2.................(1)

In your case:

u(x) = x2 + 1 .................... u' = 2x

v(x) = ln(x) ................................ v' = 1/x

Using these in (1)

df/dx = [(2x) * ln(x) - (x2 + 1) * (1/x)]/{ln(x)}2

Now simplify and continue...
Go to Top of Page

markmil2002
Average Member

USA
11 Posts

Posted - 09/18/2007 :  22:12:33  Show Profile
I've made it that far, but I dont see how to simplify. Obviously e will probably be involved to cancel ln, but I cant figure out how to apply it.


quote:
Originally posted by Subhotosh Khan

quote:
Originally posted by markmil2002

I'm trying to find the derivitive of f(x) = (x + 1)/(ln x)


After doing some math I got -2x/x but I don't think that is correct.




f(x) = u(x)/v(x)

df/dx = (u'*v - v'*u)/v2.................(1)

In your case:

u(x) = x2 + 1 .................... u' = 2x

v(x) = ln(x) ................................ v' = 1/x

Using these in (1)

df/dx = [(2x) * ln(x) - (x2 + 1) * (1/x)]/{ln(x)}2

Now simplify and continue...

Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Topic Locked
 Printer Friendly
Jump To:
Math Forums @ Math Goodies © 2000-2004 Snitz Communications Go To Top Of Page
This page was generated in 0.06 seconds. Snitz Forums 2000
testing footer
About Us | Contact Us | Advertise with Us | Facebook | Blog | Recommend This Page




Copyright © 1998-2014 Mrs. Glosser's Math Goodies. All Rights Reserved.

A Hotchalk/Glam Partner Site - Last Modified 21 May 2014