Why does invertibility of the matrix $A-\lambda I$ imply that $\lambda$ is not an eigenvalue?

450 Views Asked by At

Is it because invertibility of the matrix $A-\lambda I$ would imply that $A-\lambda I$ has a trivial null space, and thus there are no solutions to the equation $Ax-\lambda I = 0$ (other than the trivial solution $0$), and thus there are no eigenvalues? Does that line of thought make sense/are there mistakes with it?