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Théorème de récurrence double:
\begin{align*}
	\text{bijective} &\iff \forall \begin{pmatrix} \alpha \\ \beta \end{pmatrix} \in \C^2, \exists ! u \in E, \begin{cases}
		u_0 &= \alpha \\
		u_1 &= \beta \\
	\end{cases}
\end{align*}

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