Find all real values of ttt for which det(t21t)=0\det\begin{pmatrix} t & 2 \\ 1 & t \end{pmatrix} = 0det(t12t)=0
t=2t = \sqrt{2}t=2 only
t=±2t = \pm\sqrt{2}t=±2
t=2t = 2t=2 only
No real solutions