1:$ -\left( 1+\frac {R_{2}}{R_{1}}\right) \cdot \frac {R_{4}}{R_{3}}$
2:$ \left( 1+\frac {R_{2}}{R_{1}}\right) \cdot \frac {R_{4}}{R_{3}}$
3:$ -\left( 1+\frac {R_{2}}{R_{1}}\right) \cdot \left( 1+\frac {R_{4}}{R_{3}}\right) $
4:$ \frac {R_{2}}{R_{1}}\cdot \frac {R_{4}}{R_{3}}$
5:$ -\frac {R_{2}}{R_{1}}\cdot \left( 1+\frac {R_{4}}{R_{3}}\right) $