
Differential Equations Ordinary and Partial Differential Equations Math Forum 
 LinkBack  Thread Tools  Display Modes 
October 20th, 2009, 01:56 PM  #1 
Joined: Sep 2009 Posts: 51 Thanks: 0  Find the differential dy
Find the differential dy of the given function. y = 7 sqrt(x)+ 1/sqrt(x) 
October 20th, 2009, 02:23 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 5,543 Thanks: 24  Re: Find the differential dy
Find dy/dx, then multiply both sides of the equation by dx.

October 20th, 2009, 03:15 PM  #3  
Joined: Mar 2007 Posts: 428 Thanks: 0  Re: Find the differential dy Quote:
That is a good practice [technique] when doing implicit differentiation as well... 3x^2  5xy2 + y^3 ==> 6xdx  10xydy 5y^2dx + 3y^2dy = (6x  5y^2)dx + (3y^2  10xy)dy which can be written as a derivative wrt any other variable, even time ... ==> (6x  5y^2)[dx/dt] + (3y^2  10xy)[dy/dt] Or , if 3x^2  5xy2 + y^3 = 0 (6x  5y^2)dx + (3y^2  10xy)dy = 0 ==> dy/dx = ( 5y^2  6x)/(3y^2  10xy) Of course, when finding a derivative this way there would be only the one line written down in stages, not the several lines to demonstrate as above. One should never write bits and pieces, but the full expression when finding derivatives that way. Writing only as differentials, as initially, is quite legitimate.  

Tags 
differential, find 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Partial Differential Differential Equations  rishav.roy10  Differential Equations  0  August 21st, 2013 05:59 AM 
how to find a solution the differential equations  mulyak.oleksandr  Differential Equations  1  September 5th, 2012 06:17 AM 
you are given general solution  find differential equation  mbradar2  Differential Equations  7  October 12th, 2010 01:09 PM 
differential equation: find general solution  mbradar2  Differential Equations  7  September 25th, 2010 10:58 AM 
unable to find solution for a differential equation  geeth416  Differential Equations  2  December 9th, 2009 01:57 AM 