I need a small help in visual studio regarding to math..

[casper.mta]

Hello, I'm making a program to solve equation with three unknowns, I got the solution of the three simultaneous from here, I don't know how it works.
So, I faced a problem which is the 3 answers of x,y,z are wrong!!!
The Simultaneous are:
ax + by + cz = j
dx + ey + fz = k
gx + hy + iz = l

the code is:
Dim a, b, c, d, f, g, h, i, e As Integer
Dim j, k, l As Integer

Dim x, y, z As Double

a = Val(txtA.Text)
b = Val(txtB.Text)
c = Val(txtC.Text)
d = Val(txtD.Text)
e = Val(txtE.Text)
f = Val(txtF.Text)
g = Val(txtG.Text)
h = Val(txtH.Text)
i = Val(txtI.Text)
j = Val(txtA.Text)
k = Val(txtK.Text)
l = Val(txtL.Text)
x = (j * e * i + b * f * l + c * k * h - c * e * l - b * k * i - j * f * h)
y = (a * k * i + j * f * g + c * d * l - c * k * g - j * d * i - a * f * l)
z = (a * e * l + b * k * g + j * d * h - j * e * g - b * d * l - a * k * h)

txtX.Text = Convert.ToString(x)
txtY.Text = Convert.ToString(y)
txtZ.Text = Convert.ToString(z)

I would like to get a help from you guys!! Thanks in advance.

[Goggy]

I would think you would need something called a "Gaussian elimination" (Or in otherwords, some peace of serious math)
An example of doing just that is given here http://www.vb-helper.com/howto_net_g...imination.html

[casper.mta]

I don't even know what is this and how it works, I don't think it will help me
ps: the link you provided is for something different

[Goggy]

You could always copy the code, and try it.

P.s
The link i provided should do just that what you asked, solve a set of equations.

[2kaud]

It looks like the method used is by use of determinants. The calculation for x, y , z are the evaluation of one of the required determinants. However, the results obtained need to be divided by the determinate of the lhs of the equation which is

Dim t As Integer

t = a * e * i - a * h * f + d * h * c - d * b * i + g * b * f - g * e * c

so x = x / t, y = y / t, z = z / t

[casper.mta]

Like this?
t = a * e * i - a * h * f + d * h * c - d * b * i + g * b * f - g * e * c
x = (a * e * l + b * k * g + j * d * h - j * e * g - b * d * l - a * k * h) / t
y = (a * k * i + j * f * g + c * d * l - c * k * g - j * d * i - a * f * l) / t
z = (j * e * i + b * f * l + c * k * h - c * e * l - b * k * i - j * f * h) / t
In addition, x and z solutions are right but y still wrong.

[2kaud]

What is the equation you are trying to solve, what answers are you getting and what are the expected answers.

[casper.mta]

the equations:
1x+1y+1z=9
2x+1y-2z=-1
3x+1y-1z=5

The answers I get: X= 4 Y= -5 Z=2
The expected answers: X= 2 Y= 3 Z= 4

[2kaud]

From checking the determinate calculations for the equation as defined in post #1, the order of the used letters does not correlate to their usage in the calculations. The required calculations given the letters used in the equation are

t = a * e * i - a * h * f + d * h * c - d * b * i + g * b * f - g * e * c;

x = (j * e * i - j * h * f + k * h * c - k * b * i + l * b * f - l * e * c) / t;
y = (a * k * i - a * l * f + d * l * c - d * j * i + g * j * f - g * k * c) / t;
z = (a * e * l - a * h * k + g * b * k - g * e * j + d * h * j - d * b * l) / t;

From post #8, these give the required answers of x = 2, y = 3, z = 4.

From where you got the equations in post #1, the letters used don't correlate with the letters used in the equation.

[casper.mta]

First, http://www.vbforums.com/showthread.p...three-unknowns from here i got the solution for the 3 equations.
Second, I'm sorry for saying this but I tried the codes and the same answers appeared!

[Goggy]

First, http://www.vbforums.com/showthread.p...three-unknowns from here i got the solution for the 3 equations.
Second, I'm sorry for saying this but I tried the codes and the same answers appeared!

Have you tried (Downloaded) and looked the example i posted in the link?
I have, and it returned exactly what you want...

[casper.mta]

I tried to send you a private message, but, I failed. I don't know who the system which you provided works, I don't even know how to use it.

[Goggy]

I tried to send you a private message, but, I failed. I don't know who the system which you provided works, I don't even know how to use it.

At the bottom of the page, you can download the project.

When you run the project, replace all the values with the values you want, remembering to put a space between them, then click solve.

[casper.mta]

Oh, that's right bro! but my project is different!! I wanna something like the picture I provided

[2kaud]

I tried the codes and the same answers appeared

This is the c++ program I used to test.

#include <iostream>
using namespace std;

int main()
{

int a = 1,
	b = 1,
	c = 1,
	d = 2,
	e = 1,
	f = -2,
	g = 3,
	h = 1,
	i = -1,
	j = 9,
	k = -1,
	l = 5;

double x, y, z;

int		t = a * e * i - a * h * f + d * h * c - d * b * i + g * b * f - g * e * c;

		x = (j * e * i - j * h * f + k * h * c - k * b * i + l * b * f - l * e * c) / t;
		y = (a * k * i - a * l * f + d * l * c - d * j * i + g * j * f - g * k * c) / t;
		z = (a * e * l - a * h * k + g * b * k - g * e * j + d * h * j - d * b * l) /t;

		cout << "t: " << t << " x: " << x << " y: " << y << " z: " << z << endl;
}

and displays

t: -4 x: 2 y: 3 z: 4

which are the required solutions.

[Goggy]

Oh, that's right bro! but my project is different!! I wanna something like the picture I provided

Then you would have to modify the example, till it looks like you want.

[casper.mta]

Which program can I make program like the picture I uploaded with C++? I don't know anything about C++ maybe I'll need your help again :|

[Goggy]

Huh?? the example wasn't in c++, it was in vb.net.

[casper.mta]

I will try it out, but I was talking to 2kaud

[2kaud]

Which program can I make program like the picture I uploaded with C++? I don't know anything about C++ maybe I'll need your help again :|

You asked for help with the maths, not the code. The program as posted in post #15 shows the required equations and the result produced. If you change the equations in the program in post #1 you should obtain the same results. Once you have the correct maths, I would suggest that if you need programming advice you post a new thread on the relevant programming forum.

[2kaud]

Huh?? the example wasn't in c++, it was in vb.net.

Yes, but I'm c++ and used c++ to prove the maths. The equations can be easily moved to the vb program as post #1.

[2kaud]

Based upon the equations in post 15, this vb program should work - but has not been tried.

Dim a, b, c, d, f, g, h, i, e As Integer
Dim j, k, l, t As Integer

Dim x, y, z As Double

a = Val(txtA.Text)
b = Val(txtB.Text)
c = Val(txtC.Text)
d = Val(txtD.Text)
e = Val(txtE.Text)
f = Val(txtF.Text)
g = Val(txtG.Text)
h = Val(txtH.Text)
i = Val(txtI.Text)
j = Val(txtJ.Text)
k = Val(txtK.Text)
l = Val(txtL.Text)

t = a * e * i - a * h * f + d * h * c - d * b * i + g * b * f - g * e * c

x = (j * e * i - j * h * f + k * h * c - k * b * i + l * b * f - l * e * c) / t
y = (a * k * i - a * l * f + d * l * c - d * j * i + g * j * f - g * k * c) / t
z = (a * e * l - a * h * k + g * b * k - g * e * j + d * h * j - d * b * l) / t

txtX.Text = Convert.ToString(x)
txtY.Text = Convert.ToString(y)
txtZ.Text = Convert.ToString(z)

NOTE that in the code in post #1, there is an issue with j

j = Val(txtA.Text)

should be

j = Val(txtJ.Text)

[casper.mta]

How stupid am I. Thank you very much!!

[casper.mta]

@2kaud, can you try these equations?
x-y-z=-2
x+y+z=12
2x+2y=18

The answers I get: x= 14, y= 4, z= 3
The expected answers: x=5, y=4, z=3

[2kaud]

Yes. So do I. Doh!!!!

....

OK. I see the finger problem. There's been a mistype when entering from my paper.

x = (j * e * i - j * h * f + k * h * c - k * b * i + l * b * f - l * e * 1) / t

should be

x = (j * e * i - j * h * f + k * h * c - k * b * i + l * b * f - l * e * c) / t

[casper.mta]

Thank you again, sir!