2.5 Solutions by Substitutions
INTRODUCTION
We usually solve a differential equation by recognizing it as a certain kind of equation (say, separable) and then carrying out a procedure, consisting of equation-specific mathematical steps, that yields a function that satisfies the equation. Often the first step in solving a given differential equation consists of transforming it into another differential equation by means of a substitution. For example, suppose we wish to transform the first-order equation dy/dx = f(x, y) by the substitution y = g(x, u), where u is regarded as a function of the variable x.
If g possesses first-partial derivatives, then the Chain Rule gives
By replacing dy/dx by f(x, y) and y by g(x, u) in the foregoing derivative, ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access