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HP Forum Archive 06

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Dumb Question!
Message #1 Posted by Blu on 20 Oct 2001, 11:12 p.m.

Can any of the early HP desktop models solve basic Algebra equations when a variable is on either side of the equation? Also, can they handel fractions?

      
Re: Dumb Question!
Message #2 Posted by Vieira, Luiz C. (Brazil) on 21 Oct 2001, 7:38 a.m.,
in response to message #1 by Blu

Hello;

as far as I've been daring around here, the only dumb questions are those that are not made.

I know that the HP48/49 deal with fractions, and I am not aware of the new ones (HP38/39/40 and some others I read that can). They have a ->Q for ordinary fractions and a counterpart for trigonometric fractions, ->QÞ (this Þ character is intended to replace the Greek letter for PI). Both will return an algebraic that is the closest equivalent to the number in Level 1. Say: .5 ->Q '1/2'

I am not quite sure I understood the other doubt; do you mean something like 'ln(x)=2*sin(x)-y' ? Is that you mean? I believe you can always manage the expression so it ends with an equals to 0, or use EXPAND and COLLECT, available in those calculators' algebra lib. Otherwise, if the expression has an inequality (say 'sin(x)>=(3*log(x))'), algebraic procedures are a bit different.

Can you add some more information?

Thanks

      
Re: Dumb Question!
Message #3 Posted by Viktor Toth on 21 Oct 2001, 9:02 a.m.,
in response to message #1 by Blu

If you're looking for a built-in equation solver, symbolic algebra capability, or built-in fractions support, you won't find them in old HP desktops. In the form you find them in modern classroom calculators, these functions are primarily educational in purpose, whereas those old HP machines were engineering problem-solving tools.

That said, if the early machine is a programmable one, nothing prevents you from programming a solution for the problems you have in mind. A "numbers only" calculator would, of course, have no symbolic algebra capability, but it can, and has, been programmed to solve various equations and systems of equations, and also to provide number theorethical solutions, including fractions support. More advanced early desktops, such as those programmable in BASIC, could of course do more; it is possible (and not very hard, as a matter of fact) to write programs to handle symbolic expressions, for instance. I don't know if any such solutions were available, but I'd not be surprised if the answer is yes.

Viktor

            
Re: Dumb Question! More Info!
Message #4 Posted by Blu on 21 Oct 2001, 10:38 a.m.,
in response to message #3 by Viktor Toth

The desktop I am most intrested in is the 9820. Below are examples of some equations I am looking to have solved automatically. What are the earliest HPs desktop/handheld, that can solve them?

Compute and/or simplify: 9{3[2(y+1)+7]+5(y-3)}

Distribute: -3(5x+8y-4)

Factor: 12x-18y+24

Solve for X: -3x-5(x-2)=15

And the most important type would be a varible on each side: 6x+7=5x-8

Thanks Again! Blu

                  
Re: Dumb Question! More Info!
Message #5 Posted by Andrés C. Rodríguez (Argentina) on 21 Oct 2001, 11:04 a.m.,
in response to message #4 by Blu

If I recall correctly, the 9820 had an interesting feature, it allows for equations to be entered in algebraic form, and it then compile and store them in RPN, so to be more efficient both in execution speed and memory usage. To be able to show the stored equation again to the user, there was an "invisible" uncompiler, which recreates the algebraic look from the internal RPN representation. It also understood implicit multiply, so " 4x " is the same than " 4 * x "

I dont think the 9820 had any symbolic algebra capabilities built in (such as the much later HP28 and 48/49 series); and most solvers at the time were to be programmed by the user, The solvers at that time were oriented to solve f(x)=0, so it was up to the user to provide the question in this format, and to preset the constants in memory before starting the solver.

I think the first example of a multivariable, user friendly solver was the TVM function in the handheld HP-80 financial calculator. I think scientific users were believed to be more able to state problems in a less friendly manner; and so left on their own :-)

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