Substitution method for solving first order differential equation.

Description
Solving of first order differential equation by substitution method is explained. Justification of changing of variables in physics is explained as to change the units or to make the variable dimension less or to reduce or simplify the constants. There two ways of substitution that are direct and inverse substitution. Both of them are defined and explained with the help of examples. Bernouli equation and homogeneous equation are defined with examples.
Prof. Arthur Mattuck, Maths, 18.03.Differential Equations, Spring 2010: 4: First-order Substitution Methods: Massachusetts Institute of Technology: MIT Open Course Ware),http://ocw.mit.edu (Accessed November 2, 2011). License: Creative Commons BY-NC-SA: http://ocw.mit.edu/terms/#cc