nd the Thevenin's voltage across the terminals a-b for the circuit shown in Fig. 4.

To find the Thevenin's voltage across the terminals a-b for the circuit shown in Fig. 4, follow these steps:

1. Identify the circuit components and their values. This includes resistors, voltage sources, and current sources.

2. Determine the open-circuit voltage. To do this, remove any load connected across terminals a-b and calculate the voltage across these terminals. This voltage is the Thevenin's voltage.

3. If there are any dependent sources in the circuit, replace them with their equivalent values based on the given conditions.

4. Simplify the circuit by combining resistors in series or parallel, using Kirchhoff's laws.

5. Calculate the equivalent resistance seen from terminals a-b. This can be done by either simplifying the circuit further or using the appropriate formulas for series and parallel resistors.

6. Once you have the equivalent resistance, use Ohm's law (V = IR) to calculate the current flowing through the circuit.

7. Finally, use the calculated current and the equivalent resistance to determine the voltage across terminals a-b using Ohm's law again (V = IR).

By following these steps, you can find the Thevenin's voltage across the terminals a-b for the given circuit.