Using energy and momentum conservation requirements, show that a free electron cannot absorb all the energy of a photon.
Einstein energy-momentum formula:
(E)² = (mc²)² - (cp)², where m = mass, E = energy, c = speed of light, and p = momentum vector.
The Attempt at a Solution
I expanded this by setting the initial energies of the photon and electron equal to the final. However, I am not entirely sure what significant expression I'm supposed to be looking for here in order to answer this question.