I'm reading my textbook, in the Diagonalization and Eigenvalues section, and am wondering how they get this...

"λI-A =

so the general solution to (λI-A)X = 0 is X = t where t is an arbitrary real number."

The book makes it sound as if the general solution of X = t is very obvious, but I'm not seeing how it's done.

Could someone enlighten me?