DSolve and assuming: wrong solution found by Mathematica 6. A bug or
- To: mathgroup at smc.vnet.net
- Subject: [mg93425] DSolve and assuming: wrong solution found by Mathematica 6. A bug or
- From: Pianiel <pdpdel at gmail.com>
- Date: Fri, 7 Nov 2008 06:01:31 -0500 (EST)
Hi all, I tried unsuccessfully to find the solution of a differential equation using Mathematica 6.0.2.1. The given solution is wrong. Would it be possible to help me? Here is what I have done: Knowing that n is an integer, I want to solve the following differential equation: DSolve[r^2A''[r]+r A'[r]+(K^2r^2-n^2)A[r]==r( n B1- B2),A[r],r] So what I wrote is: Res=Assuming[Element[n,Integers],DSolve[r^2A''[r]+r A'[r]+(K^2r^2- n^2)A[r]==r( n B1- B2),A[r],r]] I checked using: Res /. n -> 1 And the result is Indeterminate! Sad!! (same thing with n->2 or n- >3, ...) On the contrary when I change directly the value of n in the equation and set it n=1: DSolve[r^2 A''[r] + r A'[r] + (K^2 r^2 - 1^2) A[r] == r ( 1 B1 - B2), A[r], r] Mathematica find a solution! Where is the bug? How to find the general solution with n integer for: DSolve[r^2A''[r]+r A'[r]+(K^2r^2-n^2)A[r]==r( n B1- B2),A[r],r] Is Mathematica able to do that?? Thanks somuch for your help! Pianiel