# Homework Help: -did my professor screw up the igan vector? matrices fun weee

1. Dec 11, 2005

### mr_coffee

Hello everyone, we found 3 igan values: 1, 2, 3
for the last case: 3

we came out with
0 -1 0
0 -1 0
2 -2 -2

he wrote b = 0, a = c;
then said igan vecotr is:
0
1
1

but clearly shoouldn't it be:
1
0
1
?

2. Dec 11, 2005

### shmoe

It's hard to tell exactly what's going on from what you've posted. You can always check to see if the vector you have is an eigenvector by multiplying it by your matrix.

3. Dec 11, 2005

### HallsofIvy

I hope, at least, that your professor can spell better than you can!

I have no idea why you mean by "b=0, a= c" since there were no "a", "b" or "c" in your original problem.

It would also help if you wrote out the original matrix which, I take it is:
[3 -1 0]
[0 2 0]
[2 -2 1]

because I prefer to go back to the original matrix to find the eigen value: "Ax= 3x" with that matrix gives the three equations
3x- y= 3x, 2y= 3y, and 2x- 2y+ z= 3z.
Obviously, from either the first equation or the second, y= 0. Having that, the first equation becomes 3x= 3x which is true for all x and the last equation become 2x+ z= 3z or 2x= 2z so x= z. Taking x= z= 1, gives
[1 0 1]. As much as I hate to admit it, you are right!

4. Dec 11, 2005

### mr_coffee

SCORE! haha, 4.0 here i come. Yes i do suck at spelling in a big way, its not so much spelling, its pure laziness on my part. Thanks for the help as always, :)