need help on a,b,c

this problem.) (13) (a) If p is a polynomial with real coefficients and z is a complex number such that p(z) = 0, show that p(z) = 0. (Hint: it might help to know that z . w = z . w and z + w = z + w.) (b) Using part (a), explain why if A is a square matrix with real entries and A is an eigenvalue of A, then A is also an eigenvalue of A. (c) Let A be a square matrix with real entries and suppose a is an eigenvector of A with eigenvalue 1. Show that x is an eigenvector of A with eigenvalue J