So the question is: For which values of a is the following matrix not diagonalizable? ....... 4 0 6 A = ( 2 a 3 ) ......-1 0 -1 So my first question is when is a matrix diagonalizable or not diafonalizable. The way I approached the question was to go about finding the eigenvalues and eigenvectors. p(h) = (4-h)(a-h)(-1-h)-(-1)(a-h)(6) Distributing this out gets pretty messy. So it doesn't seem like this is the right approach. Can someone help me out please? How do I go about solving this?