Let E(x)=x3+xk2−5x+7, where k is an integer.
(i) Determine all integral values of k for which E(x) is a polynomial in x. Give justification for each value.
(ii) For every permissible value of k, write the degree of the corresponding polynomial.
(iii) Find the value(s) of k for which the degree of E(x) becomes 5, and write the resulting polynomial explicitly.