Bernouilli ODE (where is my mistake?)

  • Thread starter Thread starter justaboy
  • Start date Start date
  • Tags Tags
    Mistake Ode
justaboy
Messages
13
Reaction score
0
found my mistake... thanks
 
Last edited:
Physics news on Phys.org
justaboy said:

Homework Statement


Solve the ODE
x^2y'+2xy-y^3=0



The Attempt at a Solution



x^2y'+2xy-y^3=0
Substitution:
v=y^-2
V makes the equation linear:
v'-4\frac{v}{x}=-2x^{-2}

I get:

v'+\frac{4}{x} v=-\frac{2}{x^2}
 
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...

Similar threads

Back
Top