One of the five quadratics below has a repeated root. (The other four have distinct roots.) What is the repeated root?


$\begin{align*}

&-x^2 + 18x + 81 \\

&3x^2 - 6x + 9 \\

&8x^2 - 32x + 32 \\

&25x^2 - 30x - 9 \\

&x^2 - 14x + 196

\end{align*}$