Well, you got wrong then! Without doing any calculations, your matrix has a column of 0's so its determinant is 0 which means that it must have 0 as an eigenvalue.

The eigenvalue equation is . Expanding on the last column, that is . Thus, the eigenvalues are 0, , and .

Need to find eigen vectors and matrix D, where [D= Q^(-1)AQ]

D being the diagonal matrix.

If there is any easy methodology plz suggest

Need help from eigen vectors onwards.

Thanks in advance.