Linear Algebra: Diagonalization (finding a so that matrix is diagonalizable)

207 Views Asked by At

enter image description here

I've found that the eigenvalues are 2 and 1 but how do I find a so that C is diagonalizable?

1

There are 1 best solutions below

0
On BEST ANSWER

The characteristic polynomial is $$(\lambda-1)^2(\lambda-2)$$

The algebraic multiplicity for $1$ is $2$.

Look at matrix $$C-I=\begin{bmatrix} 1 & 0 & 1 \\ 1 & 0 & a \\ 0 & 0 & 0\end{bmatrix}$$

We need the nullity of $C-I$ , which is also the dimension of eigenspace corresponding to eigenvalue $1$, to be $2$ in order to diagonalize it. The two non-zero rows should be multiple of each other.