## Different answers on different computers

I am trying to solve a question my professor posed on a simulation for my Linear Algebra and Geometry course and I get different answers depending on the pc used, I tried using MATLAB online and I got the same result I had on my installed version, a friend gets a different answer on his own PC but always consistent in the specific PCs. I understand this might have something to do with the ill conditioning of a system but the code is so brief and short, and I think the point of the question posed is that fact in the first place. The problem in question:

Let M be the matrix generated by the command magic(432), I the identity matrix and A = M + 10I. Let b be the right-hand side such that the solution of the linear system Ax = b is a vector with all elements equal to 1. Solve the linear system with the MATLAB command . Let Nr be the infinite norm of the residual b – Ax. Which is the order of Nr?"

The question is a multiple choice one and the choices are as follows:

10^-3

10^-8

10^-6

10^-1

10^-5

with 10^-8 being marked as the correct answer.

The code I used is this:

M = magic(432);

I = eye(432);

A = M + 10 * I;

x = ones(432,1);

b = A*x;

x_computed = Ab;

norm(b – A*x_computed,inf)

I do not understand what process I have to go through to stabilize this problem nor if I need to do so in the first place. Is this question just problematic with the way it is posed or is there an obvious solution to it that I as a begineer can not see?I am trying to solve a question my professor posed on a simulation for my Linear Algebra and Geometry course and I get different answers depending on the pc used, I tried using MATLAB online and I got the same result I had on my installed version, a friend gets a different answer on his own PC but always consistent in the specific PCs. I understand this might have something to do with the ill conditioning of a system but the code is so brief and short, and I think the point of the question posed is that fact in the first place. The problem in question:

Let M be the matrix generated by the command magic(432), I the identity matrix and A = M + 10I. Let b be the right-hand side such that the solution of the linear system Ax = b is a vector with all elements equal to 1. Solve the linear system with the MATLAB command . Let Nr be the infinite norm of the residual b – Ax. Which is the order of Nr?"

The question is a multiple choice one and the choices are as follows:

10^-3

10^-8

10^-6

10^-1

10^-5

with 10^-8 being marked as the correct answer.

The code I used is this:

M = magic(432);

I = eye(432);

A = M + 10 * I;

x = ones(432,1);

b = A*x;

x_computed = Ab;

norm(b – A*x_computed,inf)

I do not understand what process I have to go through to stabilize this problem nor if I need to do so in the first place. Is this question just problematic with the way it is posed or is there an obvious solution to it that I as a begineer can not see? I am trying to solve a question my professor posed on a simulation for my Linear Algebra and Geometry course and I get different answers depending on the pc used, I tried using MATLAB online and I got the same result I had on my installed version, a friend gets a different answer on his own PC but always consistent in the specific PCs. I understand this might have something to do with the ill conditioning of a system but the code is so brief and short, and I think the point of the question posed is that fact in the first place. The problem in question:

Let M be the matrix generated by the command magic(432), I the identity matrix and A = M + 10I. Let b be the right-hand side such that the solution of the linear system Ax = b is a vector with all elements equal to 1. Solve the linear system with the MATLAB command . Let Nr be the infinite norm of the residual b – Ax. Which is the order of Nr?"

The question is a multiple choice one and the choices are as follows:

10^-3

10^-8

10^-6

10^-1

10^-5

with 10^-8 being marked as the correct answer.

The code I used is this:

M = magic(432);

I = eye(432);

A = M + 10 * I;

x = ones(432,1);

b = A*x;

x_computed = Ab;

norm(b – A*x_computed,inf)

I do not understand what process I have to go through to stabilize this problem nor if I need to do so in the first place. Is this question just problematic with the way it is posed or is there an obvious solution to it that I as a begineer can not see? system, inconsistent answers MATLAB Answers — New Questions