Hello,

It doesn't matter !

Calculate the determinant of X - lambda I, that is to say the determinant of :

Code:

1-alpha-lambda alpha
beta 1-beta-lambda

add column c1 to column c2 :

Code:

1-alpha-lambda 1-lambda
beta 1-lambda

determinant=(1-lambda)(1-alpha-lambda)-beta*(1-lambda)

=(1-lambda) [ 1-alpha-lambda-beta ]

lambda is such that the determinant is = 0.

So lambda=1 or lambda=1-(alpha+beta)

These are the eigenvalues Was it clear enough ?

Then calculate the eigenvectors like you've learnt with numbers.