Re: DSolve and N do not commute

*To*: mathgroup at smc.vnet.net*Subject*: [mg40267] Re: DSolve and N do not commute*From*: Bill Rowe <listuser at earthlink.net>*Date*: Fri, 28 Mar 2003 04:32:36 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 3/27/03 at 6:51 AM, selwynh at earthlink.net (Selwyn Hollis) wrote: >Very strange... No such "bug" in Version 4.1.5 for Mac OS X: >eq := (f''[r] + 8 2^(2/3)/3 f'[r] == -8 2^(1/3)/3 f[r]) >DSolve[eq, f[r], r] >{{f[r] -> C[1]/E^((2/3)*2^(2/3)*r) + C[2]/E^(2*2^(2/3)*r)}} >DSolve[N[eq], f[r], r] >{{f[r] -> C[1]/E^(3.1748*r) + C[2]/E^(1.05827*r)}} Interesting. In Version 4.2.1 for Mac OS X this last results in {{f[r] -> C[1]/E^(3.1748*r) + (r*C[2])/E^(3.1748*r)}}