Differential Equations
Introduction

Basic Conceptions

First-Order Differential Equations

Directly Integrable Equations
  Motion of a Body - Problem 1
  Motion of a Body - Problem 2
  Motion of a Body - Problem 3
  The Spontaneous Radioactive of Substance

Separable Equations
  Motion of Particals in Viscous Fluid
  Newton's Model of Cooling
  Model of Population

Separable Equations
  Motion of Particals in Viscous Fluid
  Newton's Model of Cooling
  Model of Population

Homogeneous Equations

Linear Equations

Bernoulli Equations

Exact Differential Equations

Differential Equations of Higher Orders

Basic Conceptions
Equations of Special Kinds

Some Graphic Illustrations using MATLAB

Clich here to go to Indefinite Inegrals


Clich here to go to Definite Inegrals




Separable Equations
Real-Life Problems:   Motion of a Body - Problem 1 » Motion of a Body - Problem 2 » Motion of a Body - Problem 3 » The Spontaneous Radioactive of Substance » Motion of Particals in Viscous Fluid » Newton's Model of Cooling » Model of Population

A separable differential equation is an equation of the form

,

where f (x) and g (y) are given functions.

We can not integrate the equation immediately because the right-hand side contains an unknown function  (x) together with the function of independent variable  x.

In order to integrate this equation, it is necessary, first, to separate the factors depending on different variables, x and y:

.

Then integrate both sides to obtain the general integral of the equation:

.


A differential equation of the form

can be reduced to a separable equation by substitution  (x) :

Then the general integral can be found by integration:

Finally, we have to solve the ordinary linear equation

u = ax + by + c

with respect to  y,

,

substituting the result of integration for u.


Examples
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