# Non Square Simultaneous Equations

### #1

Posted 15 July 2005 - 03:50 AM

2x + 3y = 4

3x + 2y = 6

3x + 4y = 7

Thanks

### #2

Posted 15 July 2005 - 04:25 AM

I tried this on my HP49 (actually the HP49 emulator ) and, as expected, it will not solve symbolically because there are more variables than equations.

If you have three equations and two unknowns you either have a duplication equation in disguise, or there is no solution. If you have a duplicate equation it means that one of the equations is either a multiple of another, the sum/different of the other two, or a combination of both. The way to test for this is to solve two of the equations and see if this solution satisfies the third. If you get no solution when solving two of the equations you were unlucky and picked the "duplicate" equation. Solving a different pair should give a solution. Finally, plug the answer into the remaining equation. If it solves then you have a solution. Otherwise there is no solution.

The ClassPad can solve...

2x + 3y = 4

3x + 2y = 6

...and get the solution {x=2,y=0}. This solution does not solve the third equation, which means there is no solution.

### #3

Posted 15 July 2005 - 06:42 AM

MCFONG

### #4

Posted 19 July 2005 - 08:15 PM

.-Z coefficient is zero in all three equations, the calc must returns a MA ERROR

.- 2 of 3 equations are linear independendt, use only this two equatios that have coefficients that form a non singular matrix. the other equation is a linear combination of the previous ones..

### #5

Posted 09 August 2005 - 10:18 AM

On the other hand, a system with less equations than unknowns can be solved in ClassPad very easily. For example, the system

x+y+3x=3

x-2y-3z=6

has infinite solutions. In ClassPad, you simply use

solve({x+y+3z=3,x-2y-3z=6},{x,y})

and you get the correct solution.

### #6

Posted 09 August 2005 - 06:11 PM

Hmm, In the general case is it "No Solution", or could this be an entry error. Imagine someone enters three equations in x,y,z and only two variables (x and y) to solve for. It could be that they simply forgot to enter the 3rd variable and it is, in fact, a simple entry mistake. In this case "No Solution" would make them think they entered everything find and there is simply no solution. On the other hand, "Invalid Dimension" is a bit confusing and isn't completely correct either.The system that digitalOD gives has no solution indeed. However, ClassPad should be able to detect that, by answering something like "No Solution", instead of "Invalid Dimension".

I can see that solve is a little different from most commands that need correct argument count matching though. I can see where something like the following should solve.

solve({x+y=2, x-y=5}, {x,y,z}) {x=7/2, y=-3/2, z=z}

...or even...solve({x+y+z=2, x-y=5+z}, {x,y,z}) {x=7/2, y=-3/2-z, z=z}

### #7

Posted 09 August 2005 - 07:54 PM

Maybe a warning message (something like :"Possible entry error: 3 equations and 2 variables" - maybe something shorter) and a "No Solution" (or the solution, if it exists) is the correct answer (btw, Mathematica does not print any warning).Hmm, In the general case is it "No Solution", or could this be an entry error. Imagine someone enters three equations in x,y,z and only two variables (x and y) to solve for. It could be that they simply forgot to enter the 3rd variable and it is, in fact, a simple entry mistake. In this case "No Solution" would make them think they entered everything find and there is simply no solution. On the other hand, "Invalid Dimension" is a bit confusing and isn't completely correct either.

### #8

Posted 09 August 2005 - 08:10 PM

Maple 7 simply returned a blank line.(btw, Mathematica does not print any warning).

### #9

Posted 26 October 2005 - 09:55 PM

> eqns := { 2*x + 3*y = 4, 3*x + 2*y = 6, 3*x + 4*y = 7 };

eqns := {2*x+3*y = 4, 3*x+2*y = 6, 3*x+4*y = 7}

> [solve( eqns, {x, y} )];

[]

because the determinant is zero and no solutions exist.

If you want to be sure that no solutions exist in maple add [ , ] before and after the solve statement .

### #10

Posted 21 January 2006 - 01:38 AM

try this: solve({y=x^2,y=x},{x,y})

it should output 2 points, something like x=0 and y=0 or x=1 and y=1

all it outputs is: {y=x^2,y=x}

whats wrong? the ti-89 can solve this, I tried

### #11

Posted 21 January 2006 - 06:00 AM

Nothing is wrong. That 's just because ClassPad cannot solve non-linear system of equations automatically. I don't know whether it is available in OS 3.0.

### #12

Posted 21 January 2006 - 12:44 PM

TI 89 or its emulator?The ti-89 can solve this, I tried

### #13

Posted 21 January 2006 - 01:06 PM

### #14 Guest_Guest_*

Posted 21 January 2006 - 08:33 PM

I have seen OS 3.0, and it can do this. I don't know about OS 2.0...Hi.

Nothing is wrong. That 's just because ClassPad cannot solve non-linear system of equations automatically. I don't know whether it is available in OS 3.0.

### #15

Posted 22 January 2006 - 01:29 AM

### #16 Guest_Guest_*

Posted 22 January 2006 - 08:31 AM

It hasn't officially been released yet.OS 3.0?!? where did you get that? has it been officially released?

### #17

Posted 22 January 2006 - 09:19 AM

I have seen OS 3.0, and it can do this. I don't know about OS 2.0...

Where we can see it also?

### #18

Posted 22 January 2006 - 10:37 PM

the men that seen the os 3.00? how many changes?...any big surprise??? thanks a lot

### #19

Posted 23 January 2006 - 08:40 PM

### #20

Posted 23 January 2006 - 10:24 PM

Is this right? I think it should solve. What version of the OS are you using? Has anyone tried this in OS 2.2? (I would try it but it's hard for me to be sure I have a clean version of OS 2.2 )I found a system that it should solve but it doesn't

try this: solve({y=x^2,y=x},{x,y})

it should output 2 points, something like x=0 and y=0 or x=1 and y=1

all it outputs is: {y=x^2,y=x}

As far as this solving in OS 3.0, I can confirm that is does. OS 3.0 has a number of improvements to non-square simultaneous equations.

Still, I think this should solve in OS 2.2

### #21

Posted 23 January 2006 - 10:36 PM

Any release dates for os 3.0?

### #22

Posted 24 January 2006 - 12:47 AM

Even if I though I knew, I wouldn'tAny release dates for os 3.0?

*really*know.

### #23

Posted 24 January 2006 - 11:37 AM

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