=for timestamp
Di Dez 14 19:50:11 CET 2004

=head3 Estels Problem

M<<
{} \begin{array}{rcl|l}
{}   -\frac{y}{2y - 1} & \geq & 0; \qquad & \cdot \left(-1\right) \\
{}    \frac{y}{2y - 1} & \leq & 0; \qquad & \cdot \left(2y - 1\right) \\
{}    y                & \leq & 0; \qquad & \cdot \left(2y - 1\right)
{} \end{array}\\
{} \Rightarrow \left(y \leq 0 \wedge y \geq \frac{1}{2}\right) \vee \left(y \geq 0 \wedge y E<lt> \frac{1}{2}\right);
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