Question 1.P.41: Determine the Thevenin equivalent resistance RTh between ter......

The problem can be solved using source transformation.

This network contains only dependent source, therefore, its V_{ Th }=0 .

For finding R_{ Th } , one test voltage V is applied between terminals a and b.

Here, V=V_1 , therefore

\begin{aligned} & I=\frac{V}{100}+\frac{21 V}{250} \\ & \frac{V}{I}=R_{ Th }=\frac{500}{47}=10.6  \Omega \end{aligned}