Find the general solution of the following differential equation

Illusionist
Messages
34
Reaction score
0

Homework Statement


Find the general solution of the following differential equation:
x.(dy/dx) = y + sqrt.[(x^2) - (y^2)]


Homework Equations


I'm working through my excerise book and have been able to get through quite a few differential equations with success, but this one really does stump me. I think it's the sqrt.[(x^2) - (y^2)] that gets me confused.


The Attempt at a Solution


My first step was to divide both sides by x to get dy/dx alone, hence:
(dy/dx) = y + [ sqrt.[(x^2) - (y^2)] / x ]

This is where I begin to get lost. My natural instinct is to try and separate the x and y's but I can't seem to and the next step for is a mystery to me. I'm having a lot of troule identifying what sort of approach to use.

Any help would be very appreciated, thank you in advance.
 
Physics news on Phys.org
Illusionist said:
My first step was to divide both sides by x to get dy/dx alone, hence:
(dy/dx) = y + [ sqrt.[(x^2) - (y^2)] / x ]

Not quite. You get,

(dy/dx) = y/x + sqrt.[1 - (y/x)^2]

Try y=ux
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top