Simultaneous Equation with 4 variables, can it be don?

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Discussion Overview

The discussion revolves around solving a system of four simultaneous equations with four variables, stemming from a mathematical integration problem. Participants explore various methods for solving these equations, including substitution, elimination, and matrix approaches.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents a system of equations and inquires whether it can be solved.
  • Another participant confirms that such systems can generally be solved but notes that occasionally there may be no solution.
  • A different participant shares their experience of using substitution to eliminate variables, emphasizing the importance of the first equation in simplifying the process.
  • One suggestion involves using elementary linear algebra techniques, specifically Gauss-Jordan elimination, to find a solution more efficiently.
  • Another participant mentions using a specific software tool, Pari, to solve the equations and provides the resulting values for the variables.
  • There are multiple mentions of using a TI calculator's simultaneous equation solver, with one participant expressing concern about needing to show their work for class.
  • One participant reports using Gaussian elimination and obtaining the same results as others, while expressing a preference for this method over substitution.
  • Questions arise about the identity and functionality of the Pari software mentioned in the discussion.

Areas of Agreement / Disagreement

Participants generally agree that the system of equations can be solved, but there are differing opinions on the best methods to use, with no consensus on a single approach. Some participants prefer substitution while others advocate for matrix methods.

Contextual Notes

Some participants express frustration with the complexity of substitution and the need to show work for class assignments, indicating potential limitations in their understanding or preferences for certain solving techniques.

Who May Find This Useful

Students working on simultaneous equations, educators looking for different teaching methods, and individuals interested in mathematical problem-solving techniques may find this discussion relevant.

dan_fmx
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Hi

I am doing integration work in maths c. I have simplified the equation using long division however when I equated the answers, i got 4 simultaneous equations with 4 variables.

My equations are:

A + C = 5
A + B + 4C + D = 12
-A -B + 4C + 4D = -1
2A + B + 4D = 4

Can this be done?
 
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Yes, in general. Occasionally, such a system will have no solution.

You could use the techniques of elimination and/or substitution.
 
Hello,
Wow, this is the first time i have ever gotten to answer a question! Like the gentlemen above me said, substituting to try to eliminate variables does work, it is very annoying, and took a couple pieces of paper, but i ended up getting an answer. The key is that first equation, since it only has two variables, if you can solve for one of them variabes down the road, you will knock off an entire one. Also, I don't know if you have one, but TI 89's have a simultaneous equation solver that works awesome, real easy to use, which is how i checked my answer. Just do some substituting to solve for a certain variable and you'll definitely get it in time. we had a problem like this in math last year for extra credit, never showed us how to do it, just gave it to us... Nobody got it :wink: I'm going to not put up the answers, because it should be worked out, but if you can't get it and nobody else can give you better help soon, let me know, i'll send you the numbers.
 
If you're familiar with elementary linear algebra you could put all those equations into a matrix and use the Gauss-Jordan elimination to find the reduced-row echelon form, it's quicker than having to use substitution and elimination by hand.
 
Pari solves this with
Code:
matsolve([1,0,1,0;1,1,4,1;-1,-1,4,4;2,1,0,4],[5;12;-1;4])
 
Hey I have just looked on the TI site and found a poly nomial simultaneous equation solver and found these values. Can you tell me if you got the same? I got A=3, B=2, C=2 and D=-1. I dare say the teacher will want me to show working so the only thing I could really do is spend a nice long day of simultaneous equating?
 
CRGreathouse said:
Pari solves this with
Code:
matsolve([1,0,1,0;1,1,4,1;-1,-1,4,4;2,1,0,4],[5;12;-1;4])

What is Pari?
 
dan_fmx said:
Hey I have just looked on the TI site and found a poly nomial simultaneous equation solver and found these values. Can you tell me if you got the same? I got A=3, B=2, C=2 and D=-1. I dare say the teacher will want me to show working so the only thing I could really do is spend a nice long day of simultaneous equating?
You can easily check by substituting these values into your original equations.
 
I ended up using Gausian Elemination for the assignment and I got the same values. I know that people in the class have used the substitution method but substituiton is just impracticle and I don't have enough patients.

Thanks for all the help and ideas on how to do it

Dan
 

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