The images you've uploaded show an electrical circuit problem that involves calculating the equivalent resistance of a given circuit. The circuit consists of resistors $R_1$, $R_2$, $R_3$, and $R_4$ connected in a combination of series and parallel configurations.

Analyzing the Circuit:

1. Resistor Configuration:

   • Resistors $R_2$ and $R_3$ are in parallel.
   • The combination of $R_2$ and $R_3$ is in series with $R_4$.
   • This entire combination is then in parallel with $R_1$.

2. Resistor Values:

   • $R_1 = 6.8 \, \Omega$
   • $R_2 = 5.6 \, \Omega$
   • $R_3 = 9.1 \, \Omega$
   • $R_4 = 3.9 \, \Omega$

Steps to Find the Equivalent Resistance:

1. Find the equivalent resistance of $R_2$ and $R_3$ in parallel: $\frac{1}{R_{23}} = \frac{1}{R_2} + \frac{1}{R_3}$ $\frac{1}{R_{23}} = \frac{1}{5.6 \, \Omega} + \frac{1}{9.1 \, \Omega}$ Calculate $R_{23}$.

2. Add $R_4$ in series with $R_{23}$ to get $R_{234}$: $R_{234} = R_{23} + R_4$ Calculate $R_{234}$.

3. Finally, find the equivalent resistance of $R_{234}$ and $R_1$ in parallel: $\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_{234}}$ Calculate $R_{eq}$.

I'll go ahead and calculate these steps for you.The equivalent resistance $R_{eq}$ of the entire circuit is approximately $3.54 \, \Omega$.

Would you like more details on this calculation, or do you have any other questions?

Here are 5 related questions to consider:

1. How does the equivalent resistance change if $R_2$ and $R_3$ are swapped?
2. What would be the current flowing through the circuit if the voltage $U$ is 12V?
3. How does adding another resistor in series with $R_4$ affect the equivalent resistance?
4. If $R_1$ is removed, what would be the new equivalent resistance?
5. How can we simplify a complex circuit with more resistors?

Tip: When resistors are in parallel, the equivalent resistance is always less than the smallest individual resistance in the group.