Solution: Disconnect the resistor RL from the circuit, and the nodes A and B are located at both ends of the port. Thevenin equivalent circuit Uoc=Uab, Req=Rab of other circuits. According to the maximum power transmission theorem, when RL=Req, RL can obtain the maximum power, and the maximum power is PLM=Uoc2/(4RL). 4Ω is connected in series with 5A current source, so the voltage across 4Ω is: U=4×5=20(V), and Zuo Zheng is negative. There is no current and voltage in the 6 Ω resistor, so: Uoc=2+0+20+20=42(V). Then short-circuit the voltage source and turn on the current source. The 3 Ω resistor is also open and the 2 Ω resistor is short-circuited, which has no influence, so: req = rab = 6+4 =10 (Ω). When RL = REQ =10Ω, RL can get the maximum power, PLM = 422/(4×10) = 44.1(w).