Let $a, b, c \in (0, \infty)$ each be a D5407: Positive real number such that
| (i) | \begin{equation} 2 a + 2 b = c \end{equation} |
Then
| (1) | \begin{equation} a b \leq \left( \frac{c}{4} \right)^2 \end{equation} |
| (2) | \begin{equation} a b = \left( \frac{c}{4} \right)^2 \quad \iff \quad a = b \end{equation} |