Matrices in Matlab
Question 1:
Solve the system of equations w + 3x  2y + z = 1 w + 2x  4y  3z = 2 x + 2y + z = 4 2w + 3x  y  z = 7 The attempt at a solution To do this in matlab, this is what I will did: >> A=[1,3,2,1;1,2,4,3;0,1,2,1;2,3,1,1]; b = [1;2;4;7] >>x=inv(A)*b Then matlab should give an answer with the solutions of w, x, y and z written in a separate line…no? Question 2: Find the eigenvalues and eigenvectors of the matrix 3, 1, 0, 0 1, 5, 2, 0 0, 2, 6, 1 0, 0, 1, 2 The attempt at a solution In matlab do I do this: >>A=[3,1,0,0;1,5,2,0;0,2,6,1;0,0,1,2] ; >>[V,D]=eig(A) Then I should get an answer for V and D, and v is a matrix whose columns are the eigenvectors and D is the diagonal matrix, so we multiply the first column of V with the first diagonal of D etc… am I wrong? Question 3: Let A= 3, 4, 2, 0 1, 2, 0, 1 4, 5, 0, 3 0, 1, 4, 2 Write the Matlab commands to construct the following matrix: 3, 0, 0, 0, 3, 1, 4, 0 0, 4, 0, 0, 4, 2, 5, 1 0, 0, 5, 0, 2, 0, 0, 4 0, 0, 0, 6, 0, 1, 3, 2 3, 4, 2, 0, 5, 5, 5, 5 1, 2, 0, 1, 5, 5, 5, 5 4, 5, 0, 3, 5, 5, 5, 5 0, 1, 4, 2, 5, 5, 5, 5 The attempt at a solution In matlab should i do this: >>A=[3,4,2,0;1,2,0,1;4,5,0,3;0,1,4,2] Then to construct the other big matrix do I do this: >> B=[diag(3:6),A’;A, fives(4,4)] You’ve probably all figured that I don’t have access to matlab just now, so I would be grateful if someone who has access to matlab could just copy and paste the commands in to see if it works. Also between each question do I write clear all to clear everything before I start the question? 
For question 2, you don't have to do anything after eig.
D is a diagonal matrix of eigenvalues  just read them off the diagonal, and V is the corresponding matrix of eigenvectors  just take each column separately. (You also have the relationship A*V=V*D  this is what you may be thinking when you want to multiply...?) Qu 3 is right but for, there is no such thing as fives: use 5*ones(4,4). Qu 1 looks good too. 
ok thanx
do you know if i did Question 3 right coz i have a feeling it is wrong? 
See edit above for Qu3.

ok thanx i really appreciate your help!
and you didn't have to say 'there is no such thing' just correct me lol 
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