Norton's Theorem will show how a complex circuit can have a simple 2 resistor equivalent with a current source. If you short the output resistor and measure the short circuit current 4 Amps Short the voltage source and open the output. Measure the resistance looking in from the open output of 8 ohms. Take that measured 4 Amps and apply for the current current source and put that measured 8 ohm resistance in parallel with the original 8 ohm output resistor. You got the equivalent circuit. Shows you got the maximum power transfer to the output in the original circuit, since the parallel resistor and output are the same value on the equivalent circuit. Both circuits have 16 Volts and 2 Amps outputs
