Let $\varphi : = (1 + \sqrt{5}) / 2$ be the D2137: Basic real golden ratio such that

(i)	\begin{equation} \varphi_* : = 1 - \varphi \end{equation}

Then \begin{equation} \left\{ x \in \mathbb{R} : x^2 - x - 1 = 0 \right \} = \{ \varphi, \varphi_* \} \end{equation}