HP 50g LINSO Linear Solver for System of Equations

[JDW]

My 50g is having trouble solving a system of linear equations which Wolfram Alpha solves very easily. On the 50g, I put the following 3 equations in an Array:

SQ(X)+SQ(Y)=5
Y=SQ(X)-3
X=Y+1

I then put the following into a second array:

X
Y

I then pressed WHT-LFT-ARROW & S.SLV, then pressed the LINSO soft key. It beeps a high-pitched tone and asks "Approx. mode on?" to which I answer YES. But it then coughs up the following error:

LINSOLVE Error: Not a linear system

Here's the Wolfram Alpha solution:

http://www.wolframalpha.com/input/?i=x%5...,x%3Dy%2B1

Why can't the 50g solve it?

[Thomas Okken]

(07-14-2018 01:58 PM)JDW Wrote:  My 50g is having trouble solving a system of linear equations which Wolfram Alpha solves very easily. On the 50g, I put the following 3 equations in an Array:

SQ(X)+SQ(Y)=5
Y=SQ(X)-3
X=Y+1

That is not a system of linear equations. The error message from the calculator is correct. You're going to need a multiple-equation solver that can handle non-linear equations.

[rprosperi]

(07-14-2018 02:31 PM)Thomas Okken Wrote:  That is not a system of linear equations. The error message from the calculator is correct. You're going to need a multiple-equation solver that can handle non-linear equations.

Also, from the AUR, for LINSOLV:

Flags: Exact mode must be set (flag –105 clear)
Numeric mode must not be set (flag –3 clear).

Saying YES to "Approx. mode on?" turns-off exact mode.

[Carsen]

(07-14-2018 02:38 PM)rprosperi Wrote:  Flags: Exact mode must be set (flag –105 clear)
Numeric mode must not be set (flag –3 clear).

Saying YES to "Approx. mode on?" turns-off exact mode.

Tagging off of rprosperi, it's probably requesting to turn on approx. mode because your equation has real numbers in them and not integers. A real number is any number with a decimal point in it. Therefore, to prevent the calculator from forcing you into approx. mode, make sure that your numbers like 5, -3, & 1 have no decimal points in them at all. If you key in your equations in exact mode, then they will integers. So just switch into exact mode before keying in the equations.

As other members pointed out, this is not a linear system of equations. Use the SOLVE command (The one on the F6 key) in the S.SLV menu and you should get the answer of [X=2, Y=1] & [X=-1 Y=-2]

This is a snip of the HP 50g graphing Calculator user's guide summarizing that I found extremely useful.

[JDW]

Gentlemen, thank you for the thoughts and suggestions. The source of my pain indeed was REAL NUMBERS (those with the wicked decimal point at right). Using REAL numbers and then pressing the rightmost SOLVE soft button yields this error:



But after changing them to INTEGERS, the rightmost SOLVE button works as expected thusly:



Thank you for the guidance!