Eigenvalues

Wassup,

We're doing eigenvalues in class atm (got a test tomoz), and though I can find them for finite matrices, I'm struggling with ones which extend to the nth row:

e.g:

Find the eigenvalues of the nxn matrix:

1 1 ... 1
1 1 ... 1
...
...
...
1 1 ... 1

Any help at all is appreciated.

If you're unable to derive the general case immediately, perhaps you could gain some insight in the problem by checking it for the thew first values of n (1,2,3).