# Why do I get this error?

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Here is the function:

function [X1,X2,X] = msystem(A,B)

[~,n] = size(A);

[~,p] = size(B);

[L,U] = lu(A);

%solving for X1

X1 = inv(A)*B;

invL = [L eye(n)];

invL = rref(invL);

invL = invL(:,(n+1:n*2));

Y = invL*B;

invU = [U eye(n)];

invU = rref(invU);

invU = invU(:,(n+1:n*2));

X2 = invU * Y;

X = Y ./ U;

if (closetozeroroundoff(X1 - X2) == zeros(n,p))

disp('The solutions are the same')

else

disp('An error has been made on this exercise')

end

if (closetozeroroundoff(X1 - X) == zeros(n,p))

disp('The solutions are the same')

else

disp('An error has been made on this exercise')

end

end

##### 0 Comments

### Accepted Answer

Adam Danz
on 18 Mar 2021

Edited: Adam Danz
on 18 Mar 2021

##### 11 Comments

Adam Danz
on 19 Mar 2021

That's like asking how to make this cube look like a circle. A 4x3 matrix can never look like a 3x3 matrix without changing the data. You can remove the first row, second row, third row, or 4th row of the 4x3 matrix but now it's a completely different variable.

m = (1:4)'.*ones(1,3)

m(3,:) = [] % remove 3rd row

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