Solution
= Solution
Zero is an <eigenvalue> exactly when the <determinant> vanishes. Here $\det A=1-\alpha^2$, so
$$
\boxed{\alpha=1\quad\text{or}\quad\alpha=-1.}
$$
For either value the other <eigenvalue> is two, as follows from the <trace>.
= Solution
Zero is an <eigenvalue> exactly when the <determinant> vanishes. Here $\det A=1-\alpha^2$, so
$$
\boxed{\alpha=1\quad\text{or}\quad\alpha=-1.}
$$
For either value the other <eigenvalue> is two, as follows from the <trace>.