can you help with his exercise?

Let A=M+10I, being M the matrix generated by the command magic(432) and I the identity matrix. 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 gaussian elimination method natively implemented in MATLAB. Let N_r be the infinite norm of the residual b-Ax. Which of the following values is the closest to N_r?

(a) 5.6e-1 (b) 7.2e-5 (c) 1.2e-3 (d) 9.6e-6 (e) 8.9e-8

this is what I tried:

M=magic(432); I=eye(432); A=M+10*I;

b=sum(A,2);

[L U P]=lu(A); x=U\(L\(P*b));

nr=norm(b - A*x, inf)

Answer 1

[Sid Jhaveri]

The following links might help you:

1) https://www.mathworks.com/matlabcentral/answers/130593-hi-am-working-on-a-code-for-gaussian-elimination

2) https://www.mathworks.com/help/symbolic/rref.html

3) https://www.mathworks.com/matlabcentral/answers/43397-performing-gauss-elimination-with-matlab