I do not know how to deal with this problem. Please help me and thank you so much

21. (a) Show that if A is an m-by-n matrix and b an m-vector, b is in Range(A) [= Col(A)] if and only if rank([A b]) = rank(A), where [A b] denotes the augmented mby-(n + 1) matrix with I) added as an extra column to A. (b) If Ax = b has no solution, Show that rank([A b]) must be rank(A) + 1