Solution
= Solution
For a <matrix proportional to its transpose>, applying the <transpose> twice gives $A^T=5A$ and therefore $A=25A$. Over the <real numbers> or <complex numbers>, $24A=0$ implies
$$
\boxed{A=0.}
$$
= Solution
For a <matrix proportional to its transpose>, applying the <transpose> twice gives $A^T=5A$ and therefore $A=25A$. Over the <real numbers> or <complex numbers>, $24A=0$ implies
$$
\boxed{A=0.}
$$