How to find the integrating factor? (1st order ODE)

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SUMMARY

The discussion focuses on finding the integrating factor for the first-order ordinary differential equation (ODE) given by the expression x² + y + y²dx - x dy = 0. The integrating factor is determined to be I(x,y) = -1 / (x² + y²). Participants clarify that the methods involving (1/N)(My - Nx) = g(x) and (1/M)(My - Nx) = h(y) are not applicable due to the improper mixing of infinitesimals and non-infinitesimals in the equation.

PREREQUISITES
  • Understanding of first-order ordinary differential equations (ODEs)
  • Familiarity with integrating factors in differential equations
  • Knowledge of partial derivatives (My and Nx)
  • Basic calculus concepts, including integration techniques
NEXT STEPS
  • Study the derivation of integrating factors for first-order ODEs
  • Learn about the method of exact equations in differential equations
  • Explore the implications of mixing infinitesimals and non-infinitesimals in calculus
  • Investigate alternative methods for solving first-order ODEs, such as separation of variables
USEFUL FOR

Mathematicians, engineering students, and anyone studying differential equations who seeks to deepen their understanding of integrating factors and their application in solving first-order ODEs.

hellotheworld
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x2 + y + y2dx - x dy = 0

Integrating factor, I(x,y) = -1 / (x2 + y2)

How to find the integrating factor ?Why I cannot use below method to solve the ode ?

(1/N)(My - Nx) = g(x) , I(x,y)=exp( ∫ g(x) dx) OR
(1/M)(My - Nx) = h(y) , I(x,y)=exp( -∫ h(y) dy)
 
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hellotheworld said:
x2 + y + y2dx - x dy = 0
That equation makes no sense. You cannot mix infinitesimals and non-infinitesimals like that.
 
hellotheworld said:
x2 + y + y2dx - x dy = 0
Did you mean ##(x^2 + y + y^2)dx - x dy = 0##?
hellotheworld said:
Integrating factor, I(x,y) = -1 / (x2 + y2)

How to find the integrating factor ?Why I cannot use below method to solve the ode ?

(1/N)(My - Nx) = g(x) , I(x,y)=exp( ∫ g(x) dx) OR
(1/M)(My - Nx) = h(y) , I(x,y)=exp( -∫ h(y) dy)
 

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