1) Use I = to find a current to plot then draw slope line to it from axis (0,0)
2) trial and error find point on slop with highest power out (highest possible voltage and current)
3) On graph where current = 0
4) On graph were voltage = 0
5) use r = V/I numbers to use are found from maximum power outage
6) formula used for both r = V/I
For Effecive series draw horizontal tangent line across the top of curve to end of graph contrast the line and the curves voltage and current.
For effective stunt resistance draw a vertical tangent line straight up from the endpoint of the curve compare the line and the curve, find where the voltage and the current interects and compare it too the curve.
7) Use data found from Maximum power and open circuit and short circuit.