4. [10 marks] Prove that for any set A, A SA. Functions] [10 marks] Determine whether each of these functions from Z to Z is one-to-one (i.e. injective) or onto (i.c., surjective), both or none. Justify your answer. 5. a) f(n)-3n2-1 b) f(n)-5 1Find fog and gef wheref(x) = x. 1 and g()-( tions from R to [ 10 marks R. 6. ? are func