HP Forum Archive 14

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solving linear systems on a 48G+ Message #1 Posted by Henrik on 17 June 2004, 11:30 a.m. Hi, has anyone tried to solve a linear equation system on a 48G+? If I do it according to the manual it won't work: Here an easy example: 0.5x - 12.5y = 0 -2.6x + 65y = 0 For x the result should be 5, for y 0.2 If I use the linear systems function in the solve menu I am asked to enter my coefficients and constants. I do this in the matrix mask, then I go to the x-line and press solve, all as stated in the manual. All I get out is O 0 no matter what I have entered. Thanks for any hints!

Re: solving linear systems on a 48G+ Message #2 Posted by Raul Lion on 17 June 2004, 12:36 p.m., in response to message #1 by Henrik Your system has infinite solutions x=25*y. You posted two of them: 0,0 and 5,0.2 I recommend install Erable... look in hpcalc.org Edited: 17 June 2004, 12:39 p.m.

Re: solving linear systems on a 48G+ Message #3 Posted by Norris on 17 June 2004, 1:17 p.m., in response to message #2 by Raul Lion Erable is powerful but also very large and complex; it will consume nearly all of the memory on a 48G+. Another well-regarded alternative is SolveSys, a small, easy-to-use simultaneous equations solver that handles both linear and nonlinear equations. Both can be downloaded from hpcalc.org

Re: solving linear systems on a 48G+ Message #4 Posted by Raul Lion on 17 June 2004, 4:27 p.m., in response to message #3 by Norris You are right.. I was thinking in the symbolic solver power not in the memory needed :-(

Re: solving linear systems on a 48G+ Message #5 Posted by Tizedes Csaba [Hungary] on 17 June 2004, 12:43 p.m., in response to message #1 by Henrik Hello, the problem with your example is the two equation is not independents! Look, this is the simpliest answer: eq1: 0.5 * x - 12.5 * y = 0 eq2: -2.6 * x + 65 * y = 0 if you multiple eq1 with -5.2, you will get the eq2. I dont want to digging into the depth of linear algebra, and my english is too poor for the correct answering. The {0 0} solution is correct - in linear algebra in this case called 'trivial solution'. Oh, why I can't to speak english...!? :) Csaba to delete: 10110

Re: solving linear systems on a 48G+ Message #6 Posted by John on 17 June 2004, 12:49 p.m., in response to message #5 by Tizedes Csaba [Hungary] Csaba: Your English is just fine. In fact it is much better than my Hungarian, which I don't speak at all. Fortunately we both speak mathematics - the truly universal language.

Re: solving linear systems on a 48G+ Message #7 Posted by bill platt (les Estats Unis d'Amerique) on 17 June 2004, 1:35 p.m., in response to message #5 by Tizedes Csaba [Hungary] Hi Tizedes, We like your English just fine (and your maths is good, too!). I wonder if Henrik fell into a math-trap---this will happen every time you try to "make up" two equations----it always works better with a real problem---like for instance a loads and moments calculation---they will reliably produce nice linear tw ovariable systems. Best regards, 1234 Bill

Re: John and Bill Message #8 Posted by Tizedes Csaba [Hungary] on 17 June 2004, 3:18 p.m., in response to message #7 by bill platt (les Estats Unis d'Amerique) Hello John and Bill, thank you, but I know I must to learn more grammar, I just places words in a row... Grammatics is not math and engineering, so it's very slowly downloadable into my brain... ;) Csaba to delete: 10110

Re: solving linear systems on a 48G+ Message #9 Posted by Bob on 17 June 2004, 3:21 p.m., in response to message #1 by Henrik This is why I still find it easier to solve these problems by hand than put them into a solver. I can always backtrack, check my solution, and, if I get nonsense answers, I have a reasonable chance of spotting it. I am usually faster doing so as well. (I've proven it during my preparation for my PE exams where time is always a factor.) Obviously, larger linear systems are another story, but then, I would not use a 48G+ for those either.

Re: solving linear systems on a 48G+ Message #10 Posted by Harrington on 17 June 2004, 8:12 p.m., in response to message #9 by Bob My consideration will be gentlemen write a little program for this math stricken men.... That will do the same it should be easy... look at how many ans this and none try a simple program for him. To the linear algebra man you don know what you looking for how do you want the calculator to make much sense... atleast try sloving the problem with hand ...

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