February 11th, 2014, 06:21 PM  #1 
Member Joined: Feb 2014 Posts: 91 Thanks: 1  I'm Missing something
A bicyclist is riding on a path modeled by the function f(x) = 0.04(8x  x^2) where and are measured in miles. Find the rate of change of elevation at x = 2 Here are the steps I've taken before I got stuck. I) f(x) = 0.04(8x  x^2) II) f(x) = 0.32x  0.04x^2 III) f^1(2) = lim 0.32(2 + h)  0.04(2^2)/h IV) f^1(2) = lim 0.64 + 0.32h  0.08/h What's my next step from this point. I think I'll be able to figure it out from there. 
February 12th, 2014, 03:57 PM  #2  
Global Moderator Joined: May 2007 Posts: 6,581 Thanks: 610  Re: I'm Missing something Quote:
If that is correct, then f'(x) = .32  .08x, so f'(2) = .16 (rate of change of elevation).  
February 12th, 2014, 04:35 PM  #3  
Math Team Joined: Sep 2007 Posts: 2,409 Thanks: 6  Re: I'm Missing something Quote:
Quote:
Quote:
f'(2)= lim [f(2+h) f(2)]/h. You don't have the "2+h" in the square f'(2)= lim [{.32(2+ h) .04(2+h)^2} {.32(2) .04(2^29}]/h= lim [{.64 .32h .04(4+ 4h+ h^2)} {.64 .16}]/h Reduce that. Notice that the constant terms, .64 .04(4) (.64+ .16), cancel so every term involves an "h". Cancel the "h" in the denominator and take the limit as h goes to 0. Quote:
 

Tags 
missing 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
What am I missing here??!!  pd97531  Elementary Math  2  November 29th, 2012 08:06 AM 
What I'm Missing  Revo  Elementary Math  8  February 3rd, 2012 07:57 AM 
What am I missing  oaktree68  Algebra  1  September 28th, 2010 09:44 AM 
missing?  metallica fish  Advanced Statistics  0  August 24th, 2009 01:21 PM 
What am I missing here?  brunojo  Number Theory  1  June 15th, 2009 07:35 PM 