CAS: solve solutions

08252016, 07:18 PM
(This post was last modified: 08262016 11:43 AM by compsystems.)
Post: #1




CAS: solve solutions
hpprime
solve(((x+5)*e^x) = ((x+5)*e^(2*x))) [ENTER] returns > {0} // one answer why the CAS returns only one answer? Expanded form expand( (x+5)*e^x) = (x+5)*e^(2*x) ) [ENTER] returns > x*e^x+5*e^x = x*e^(2*x)+5*e^(2*x) mathematica returns 3 answers https://www.wolframalpha.com/input/?i=(x...*e%5E(2*x) [ENTER] returns > x = 5 // real solution x = 0 // real solution x = 2*π*i*n where n ∈ Z // a symbolic answer =] 

08252016, 08:22 PM
Post: #2




RE: CAS: solutions
I tried it (with different parentheses) and, after a cryptic warning, got the same answer Mathematica did.


08262016, 07:49 AM
Post: #3




RE: CAS: solve solutions  
08262016, 01:12 PM
Post: #4




RE: CAS: solve solutions
Have you select Complex? (CAS settings)
I have the same answer as Steve (10077) — Dirk Hartland 

08262016, 01:17 PM
Post: #5




RE: CAS: solve solutions
but the answer (5) is not complex output is real number


08262016, 01:50 PM
Post: #6




RE: CAS: solve solutions
Have you try it?
Deselect complex, answer is {0} Selected complex, answer is {5 0} — Dirk Hartland 

08262016, 03:20 PM
Post: #7




RE: CAS: solve solutions
Specifying a range works here as well.
10..10 returns 5,0 also Perhaps bernard can shed some light as to why it only finds the one solution in this case without specifying a range. TW Although I work for the HP calculator group, the views and opinions I post here are my own. 

08262016, 10:07 PM
Post: #8




RE: CAS: solve solutions
(08262016 07:49 AM)retoa Wrote: Hi Steve! solve((x+5)*e^x = (x+5)*e^(2*x),x) (note that on the calculator I didn't have the parentheses around the 2*x term since in textbook form it was obvious that the whole term was part of the power of e) My settings were Exact on, Complex on, Use Sq on, Use i off, Principal off and increasing off. The warning I got was: Warning: solving x in equation
x*(e^x)^2+x*e^x5*(e^x)^2+5*e^x=0 Anybody know what this warning means? 

08262016, 10:37 PM
Post: #9




RE: CAS: solve solutions
Right, with complex on it gives both answers.
Does it need to use complex numbers for some substitution? 

08272016, 06:16 AM
Post: #10




RE: CAS: solve solutions
With the current version of Xcas I get 5 and 0 for solve((x+5)*e^x = (x+5)*e^(2*x),x). I don't know why it does not work for older versions of giac.


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