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How to write cramer's rule 3x3 by matlab ?

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ENG. Mohamed Ibrahim
回答： Asif Iqbal 2022-1-28
How to write cramer's rule 3x3 by matlab ?
  1 个评论
James Tursa
James Tursa 2016-3-10
What have you done so far? Do you know how to replace elements in a matrix with other elements? Do you know how to use a for loop? Do you know how to calculate the determinant of a matrix?

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回答（3 个）

Explorer
Explorer 2016-3-10
编辑：Explorer 2016-3-10
Question: Find the system of Linear Equations using Cramers Rule:
2x + y + z = 3
x – y – z = 0
x + 2y + z = 0
The above example is taken from http://www.purplemath.com/modules/cramers.htm
% Demo Code:
A = [2 1 1; 1 -1 -1; 1 2 1] % Coefficient Matrix
X = [3; 0; 0]
Ax = [3 1 1 ; 0 -1 -1;0 2 1 ]
Ay = [2 3 1; 1 0 -1; 1 0 1]
Az = [2 1 3; 1 -1 0; 1 2 0]
detA=det(A)
x = det(Ax)/detA
y = det(Ay)/detA
z = det(Az)/detA
  5 个评论
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Robert Strunz
Robert Strunz 2021-1-15
编辑：Robert Strunz 2021-1-15
Is this a better solution,my matrix is called NAM, and the column vector is I ?
% Create a modified NAM for node b by inserting I into the first column.
mNAM_b = [I NAM(:,2:3)]
delta_b = det(mNAM_b)
VB = delta_b/delta_0
% Create a modified NAM for node c by inserting I into the second column.
mNAM_c = [NAM(:,1) I NAM(:,3)]
delta_c = det(mNAM_c)
VC = delta_c/delta_0
% Create a modified NAM for node e by inserting I into the third column.
mNAM_e = [NAM(:,1) NAM(:,2) I]
delta_e = det(mNAM_e)
VE = delta_e/delta_0
James Tursa
James Tursa 2021-1-15
Rather than creating the modified matrix with concatenation, a direct assignment of the column:
k = the column number to replace
mNAM = NAM;
mNAM(:,k) = I;
This could easily be put into a loop.

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Faith Ira Daro
Faith Ira Daro 2021-11-24
given the linear equations:
3x+2y = -5
-5x+7y=1
solve for the values of x and y using cramers rule
Asif Iqbal
Asif Iqbal 2022-1-28
% Demo Code:
A = [2 1 1; 1 -1 -1; 1 2 1] % Coefficient Matrix
X = [3; 0; 0]
Ax = [3 1 1 ; 0 -1 -1;0 2 1 ]
Ay = [2 3 1; 1 0 -1; 1 0 1]
Az = [2 1 3; 1 -1 0; 1 2 0]
detA=det(A)
x = det(Ax)/detA
y = det(Ay)/detA
z = det(Az)/detA

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