1. ## Gauss elimination method

How can I solve this problem by using Gauss elimination method? Thanks alot!

3x+ y -5z -w=0
-2x +4y +z -2w= 2
2x+ 2y -3z +5w= 7
-3x +2y -z +4w=6

2. ## Re: Gauss elimination method

Originally Posted by math88
How can I solve this problem by using Gauss elimination method? Thanks alot!
3x+ y -5z -w=0
-2x +4y +z -2w= 2
2x+ 2y -3z +5w= 7
-3x +2y -z +4w=6
Have a look at this webpage.

3. ## Re: Gauss elimination method

Thank you. The webpage is very helpful.

4. ## Re: Gauss elimination method

Originally Posted by math88
If you will learn to use it, it can save you a lot of time.

5. ## Re: Gauss elimination method

Hi,

I have following bivariate data.
(y) 800 1000 1200
(x)
1150 1380.4 1500.2 1614.5

1200 1377.7 1499.0 1613.6

1250 1375.2 1497.1 1612.6

The correct solution for this interms of bivariate equation (a+bx+cy+dx^2+ey^2+fxy)
914.033 - 0.0205000x + 0.645500y - 0.000040000x^2 - 0.000077500y^2 + 0.000082500xy.

But when i use matlab c=inv(A) * b, i get coefficient which produces more errors. What i am looking for is high accuracy interms of 0.5 error or less than that. Is there any other way i can calculate the coefficients? pls suggest.

6. ## Re: Gauss elimination method

Hi,

I have following bivariate data.
(y) 800 1000 1200
(x)
1150 1380.4 1500.2 1614.5

1200 1377.7 1499.0 1613.6

1250 1375.2 1497.1 1612.6

The correct solution for this in terms of bi-variate equation (a+bx+cy+dx^2+ey^2+fxy)
914.033 - 0.0205000x + 0.645500y - 0.000040000x^2 - 0.000077500y^2 + 0.000082500xy.

But when i use matlab c=inv(A) * b, i get coefficient which produces more errors. Following are the coefficient produced by matlab

a = -8.12E+03
1.52E+01
4.61E-01
-6.46E-03
-8.56E-05
2.50E-04

What i am looking for is high accuracy in terms of 0.5 error or less than that. Is there any other way/tool i can calculate the coefficients with very high accuracy? pls suggest.

matlab code:
a=[9 10800 9000 12975000 9240000 10800000
10800 12975000 10800000 15606000000 11088000000 12975000000
9000 10800000 9240000 12975000000 9720000000 11088000000
12975000 15606000000 12975000000 18792000000000 13321000000000 15606000000000
9240000 11088000000 9720000000 13321000000000 10450000000000 11664000000000
10800000 12975000000 11088000000 15606000000000 11664000000000 13321000000000];

b = [13470.3
16163800
13611800
19418500000
14112200000
16333700000];

ans = inv(a)*b