What Determines Regular and Irregular Singular Points in Differential Equations?

  • Thread starter Thread starter Rijad Hadzic
  • Start date Start date
  • Tags Tags
    Points Regular
Rijad Hadzic
Messages
321
Reaction score
20

Homework Statement


Determine singular points of given DE. Classify as regular or irregular

(x^3 -2x^2 + 3x)^2 y'' + x(x-3)^2 y' + (-x-1)y = 0

Homework Equations

The Attempt at a Solution



From the polynomial infront of y'' I get

x^2 (x^2 -2x + 3)^2

right out of the bat I can see that x = 0 is going to be a regular point.

the zeros of x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2}

so since the denominator of y' will have x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2} to the second power, can I say that x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2} are the irregular points then?
 
Physics news on Phys.org
Rijad Hadzic said:

Homework Statement


Determine singular points of given DE. Classify as regular or irregular

(x^3 -2x^2 + 3x)^2 y'' + x(x-3)^2 y' + (-x-1)y = 0

Homework Equations

The Attempt at a Solution



From the polynomial infront of y'' I get

x^2 (x^2 -2x + 3)^2

right out of the bat I can see that x = 0 is going to be a regular point.

the zeros of x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2}

so since the denominator of y' will have x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2} to the second power, can I say that x^2 -2x +3 = 1\frac +- \frac {8^{1/2}}{2} are the irregular points then?
It is not correct to say ##x^2 -2x +3 = 1 \pm\frac {8^{1/2}}{2}##. I think what you mean is ##x^2 -2x +3 = (x-1 + \frac {8^{1/2}}{2})(x-1 - \frac {8^{1/2}}{2})##. That is still not right, though, because you have made a mistake in solving for the roots of ##x^2-2x+3##.
 
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