How to solve first Order Differential Equation | lesson 2

preview_player
Показать описание
Definition of Exact Equation

A differential equation of type

Mdx+Ndy=0 where M and N are all functions of x

is called an exact differential equation if there exists a function of two variables F(x,y) with continuous partial derivatives such that

dF(x,y) = Mdx+Ndy.

The general solution of an exact equation is given by

F(x,y)=C,

where C is an arbitrary constant.

Test for Exactness

Let functions M and N have continuous partial derivatives in a certain domain D. The differential equation Mdx+Ndy =0 is an exact equation if and only if

∂M/∂y=∂N/∂x.

Algorithm for Solving an Exact Differential Equation

First it’s necessary to make sure that the differential equation is exact using the test for exactness:

∂M/∂y=∂N/∂x.

Then we write the system of two differential equations that define the function F(x,y):

∂F/∂x=M and ∂F/∂y=N

Integrate the first equation over the variable x. Instead of the constant C, we write an unknown function of y:

F(x,y) = ∫M(x,y)dx.

The we differentiating with respect to y, we substitute the function F(x,y)into the second equation:

∂F/∂y = ∂/∂y[∫M(x,y)dx+φ(y)]=N(x,y).

From here we get expression for the derivative of the unknown function φ(y):

φ′(y)=M−∂F/∂y

By integrating the last expression, we find the function φ(y) and, hence, the function F(x,y):

F(x,y) = ∫Mdx+φ(y).

The general solution of the exact differential equation is given by

F(x,y)=C.

If you find this video interesting, kindly subscribe to my channel for more exciting Maths tutorials.




Рекомендации по теме
Комментарии
Автор

Nice work again🙂👨‍🏫 The textbook I teach from would also called that a separable differential equation as you had in the 2nd line. Once the variables are separated you can integrate both sides. It is always fun when you have multiple tools to choose from to solve the same problem.

profrobbob
Автор

Your channel is really incredible with alot of inspiring video

VICASTUTORIAL
Автор

Thank you for another great video on solving Exact Differential Equations.

georgesadler
Автор

Can we solve this particular equation by separation of variables method

edu_phelia
Автор

Big up brother, All the way from Canada thanks bro

harounmsimbe
Автор

Determine the most general function M and N such that the equations M(x, y)dx + (2xy³-x⁴y)dy is exact.

oyedokun
Автор

How did you appear in the video screen just like that pls spell out. I guess you have got some powers 😂😂😂

CindySmith-cpor
Автор

Determine the most general function M and N such that the equations M(x, y)dx + (2xy³-x⁴y)dy is exact.

oyedokun
Автор

How did you appear in the video screen just like that pls spell out. I guess you have got some powers 😂😂😂

CindySmith-cpor