Substitution differential equation problem

In summary, the conversation discusses solving the differential equation y' = y/x + 1/y. It involves setting a substitution v = y/x and taking the integral of both sides, resulting in the solution y = sqrt(x) * sqrt(x*c - 2). The person realizes they made a substitution error and needed to substitute v = y^2 to get the correct solution.
  • #1
Michels10
18
0
Solve y' = y/x + 1/y


I get a similar answer to the correct one but I believe I am making a substitution error. Here is my attempt:




dy/dx = y/x + 1/y

set v = y/x

equation now becomes: v + x(dv/dx) = v + 1/(x*v)

reduces to: dv/dx = 1/(x^2 * v)

Now the equation is seperable, so I separate and take the integral of both sides yielding:

v = (sqrt(-2) * sqrt(x*c - 1))/sqrt(x)

--even if i substitute v = y/x back in it doesn't come out to be the correct solution of:

y = sqrt(x) * sqrt(x*c -2)



Any insight would be great!
 
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  • #2
Nevermind, solved it. Needed to substitute v=y^2.

Thanks!
 

What is a substitution differential equation problem?

A substitution differential equation problem is a type of mathematical problem where a function is substituted into a differential equation in order to solve for the value of the function. This method is often used when the differential equation is difficult to solve directly.

What is the difference between a substitution differential equation and a regular differential equation?

The main difference between a substitution differential equation and a regular differential equation is the method used to solve them. In a regular differential equation, the goal is to find the function that satisfies the equation, while in a substitution differential equation, a known function is substituted into the equation to find the value of the function.

What are the advantages of using substitution to solve a differential equation?

Using substitution to solve a differential equation can be advantageous because it can simplify the equation and make it easier to solve. It can also be used to solve equations that are difficult or impossible to solve using other methods.

What are some common techniques used in substitution differential equation problems?

Some common techniques used in substitution differential equation problems include using trigonometric identities, logarithms, and power series. These techniques can help simplify the equation and make it easier to solve.

Are there any limitations to using substitution to solve a differential equation?

While substitution can be a useful method for solving differential equations, it is not always applicable. Some differential equations may not have a known function that can be substituted, or the substitution may lead to a more complex equation that is still difficult to solve.

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