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Friday, July 18, 2014

Solving Equations - Homogeneous Functions, 10

Category: Differential Equations

"Published in Newark, California, USA"

Find the general solution for


Solution:

Consider the given equation above  


Did you notice that the given equation cannot be solved by separation of variables? The first and second term are the combination of x and y in the group and there's no way that we can separate x and y.  

This type of differential equation is a homogeneous function. Let's consider this procedure in solving the given equation as follows   







Let


so that

 
Substitute the values of y and dy to the given equation, we have 









The resulting equation can now be separated by separation of variables as follows  




Integrate on both sides of the equation, we have 





Next, we need to solve for the value of A, B, and C by partial fractions as follows



Equate the coefficients for u², we have



Equate the coefficients for u, we have


Equate the coefficients for u0, we have 


Then it follows that


Substitute the value of A, B, and C to the above equation, we have








Take the inverse natural logarithm on both sides of the equation, we have




But



Hence, the above equation becomes











where D = C².

Therefore, the general solution is