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# HP Prime cannot solve system of equations in solve app

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HP Prime

I'm trying to solve the sysem of equations below. Three equations, three unknowns. This is for an engineering exam. My frustration is that wolfram alpha solves these fine but my HP Prime will not. It just displayes " cannot find solution"... Obviously wolfram works for studying but I need to be able to solve these on my calcultor during exams..  The srangest part is that the  first attempt at solving, the calculator got the correct answers and ever since then it just displays "cannot find solution". I'm entering these into the solve app. Any ideas why wolfram alpha beezes through these yet the HP prime cannot solve them? Processing power?

1.)    -303.325x + 50y -30z = 0

2.)      50x -33.325y -50z = 0

3.)      x^2  +  y^2  +  z^2  = 1

Wolfram displays the answers as:   X = -.1876...   Y = -.8935...   Z = .4079...

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Strange; my Prime's Solve app, using firmware version 2016 12 08 (11226), solves that system without any problem.  Which firmware version does your Prime have?  (Home, Help, Tree, up-cursor, OK).

-Joe-
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Well i'm going to guess that's the issue. I havent updated my calculaor in a long time... or ever.. Whoops. I'll try updating it when I get home. Thanks for the help!

Software Version: 2013 8 13 (5106)

CAS Version 1.1.0

Native OS Vers. V0.025.5106

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Good news! I entered your system into a Prime whose firmware is version 2014 7 2 (6031), and -- like your even-older version -- it says "Cannot find solution" if all three variables are zero.  However, if you enter guesses (e.g. 1 for X and 1 for Y) then it does find a solution. This verifies that the problem you're experiencing is indeed due to obsolete firmware.

The latest firmware solves your system even when all three variables are zero.  However, keep in mind that some systems are very hard to solve, and will require you to help it along by providing guess(es).  Whenever the solver says that it can't find a solution, try giving it a nudge by providing one or more guesses.

Disclaimer: I don't work for HP. I'm just another happy HP calculator user.

-Joe-
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I updated and it's working just fine, thanks for the help! That's interesting that a nudge makes the difference. The system is solving for the 3 components of a unit vector so they're all between 0 and +/- 1. Curious why it figures it out with a guess of 1 but not zero. Beggers can't be choosers i suppose. Assuming it's just the way the fxn runs but that's not my major 🙂

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