non-inverting input of the opamp, that will get duplicated at the output and force 1V voltage across the 4k resistor, and then adjusting the 240k resistor doesn't impact the 1V across the 4k... great circuit, thanks
Almost.
The voltage on the non-inverting input of the opamp won't get
duplicated at the output, the output will do whatever it has to do in
order to make the voltage on the inverting input equal to the voltage
on the non-inverting input