Solve in c applying the Gauss method, the system of equations: -x+4y-7z=5 x-y-2z=-2 2y-6z=2

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embizze's profile pic

embizze | High School Teacher | (Level 2) Educator Emeritus

Posted on

First we create the augmented matrix with the coefficients:

`[(-1,4,-7,|,5),(1,-1,-2,|,2),(0,2,-6,|,2)]` Now we row reduce:

`=>[(1,-4,7,|,-5),(0,3,-9,|,7),(0,2,-6,|,2)]` R1*(-1);R1+R2;R3

`=>[(1,-4,7,|,-5),(0,1,-3,|,7/3),(0,0,0,|,4)]` R1;1/3R2;-3/2R3+R2

Since the bottom row has all zeros in the coefficient slots there are no solutions. (The bottom constraints are parallel planes)



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oldnick | (Level 1) Valedictorian

Posted on

System hasn't solutions for:

`det [[-1,4,-7],[1,-1,-2],[0,2,-6]]=0`


Columns are dipendent, indeed, if set a system for the first two columns:



That has solution:    `lambda_1=-5`  `lambda_2=-3`

If we  apply that ones at the third row:

`0 xx lambda_1 + 2 lambda_2=0xx (-5)+2 xx (-3)=-6`

That shows third line is in line of dipendence of columns and determinant is 0 

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