Calculate the first-order shift to the energy of the ground state and first excited state of a particle of mass m in the one-dimensional infinite square well
V(x)={0∞0<x<Lelsewhere
of (a) the constant perturbation H^1=V1 and (b) the linearly increasing perturbation H^1=εE1(0)x^/L, where E1(0) is the unperturbed energy of the ground state and ε≪1.