
Calculus Calculus Math Forum 
 LinkBack  Thread Tools  Display Modes 
October 3rd, 2014, 08:08 PM  #1 
Member Joined: Sep 2014 From: Cambridge Posts: 64 Thanks: 4  Derivative without using properties of logarithms
y = ln[(2x+8 ) / ( 8x+25)] After deriving, I come to $\displaystyle \frac{1}{\dfrac{2x+8}{8x+25}}\left(\frac{14}{(8x+25)^2}\right)$ Could someone fully show me how to simplify this further? EDIT: I get to negative 7/(x+4)(8x+25)^3 but wolfram says that ^3 is not supposed to be there for (8x+25).... Last edited by MarkFL; October 3rd, 2014 at 10:47 PM. Reason: Restore gutted content 
October 3rd, 2014, 10:45 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,155 Thanks: 466 Math Focus: Calculus/ODEs 
What you want is: $\displaystyle \frac{1}{\dfrac{2x+8}{8x+25}}\left(\frac{14}{(8x+25)^2}\right)=\frac{2\cdot7(8x+25)}{2(x+4)(8x+25)^2}=\frac{7}{(x+4)(8x+25)}$ By the way, please do not edit a post once you have solved the question to remove the original question. Gutting a thread this way leaves behind a useless post. 

Tags 
derivative, logarithms, properties 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
properties of logarithms  bongantedd  Algebra  1  February 1st, 2014 12:55 PM 
Some log properties  tiba  Algebra  8  June 27th, 2012 03:23 AM 
Need help with some bigO properties proofs  ran  Computer Science  1  June 1st, 2010 12:53 PM 
properties of logarithms  imcutenfresa  Calculus  1  November 15th, 2009 01:42 PM 
properties of the derivative... grade 12 calculus...  savica  Calculus  2  June 24th, 2009 04:50 PM 