Can someone help me solve the problem 3.4 (It is a Quantum Mechanics question)

3.4 A particle with mass m is moving in one dimension near the speed of light so that the relation E = p-/2m for the kinetic energy is no longer valid. Instead, the total energy is given by E- = p?c' + mic+ Hence, we can no longer use the Schrodinger equation. Suppose the wave function (x, t) for the particle is an eigenfunction of the energy operator and an eigenfunction of the momentum operator, and also assume that there is no potential energy V. Derive a linear differential equation for V (x, f). 3.5 A particle with mass m is moving in one dimension in the potential V (x). The particle is in a state of definite energy E, but it is not in a state of definite momentum p. Show that 2m + (V (x)) = E