# Eigenvector help

• May 16th 2009, 05:43 PM
chuckienz
Eigenvector help
Ok. I have used matlab to help with finding the eignvectors for a given matrix. I have got the eigenvalues already.

the problem Im having is I have got this matrix as the result of doing row operations
ans =
1 0 -1
0 1 1
0 0 0
Now, can I jut read off the diagoinal for the eigenvectors or do I have to solve the equations below

X + 0y –z = 0
0 +y +z = 0
0 + 0 +0 = 0
Thanks
• May 17th 2009, 04:57 AM
Rapha
Quote:

Originally Posted by chuckienz
Now, can I jut read off the diagoinal for the eigenvectors

Never heard of that before.

Quote:

Originally Posted by chuckienz
or do I have to solve the equations below

X + 0y –z = 0
0 +y +z = 0
0 + 0 +0 = 0
Thanks

Yep, that's correct. That would work.
• May 17th 2009, 10:45 AM
SydneyBristow
I think the only time the Eigenvalues are on the diagonal is when you have Diagonalized the matrix. ... Then the matrix is just an n by n with eigenvalues on the diagonal.
• May 17th 2009, 11:03 AM
HallsofIvy
Quote:

Originally Posted by chuckienz
Ok. I have used matlab to help with finding the eignvectors for a given matrix. I have got the eigenvalues already.

the problem Im having is I have got this matrix as the result of doing row operations
ans =
1 0 -1
0 1 1
0 0 0
Now, can I jut read off the diagoinal for the eigenvectors or do I have to solve the equations below

X + 0y –z = 0
0 +y +z = 0
0 + 0 +0 = 0
Thanks

Yes, you need to solve the equations. Here, that gives x= z and y= -z so any eigenvector can be written <z, -z, z>= z<1, -1, 1>. No, you cannot just "read off" the eigenvectors.