7. (10pts) Determine whether f is a function or not. Justify your answer. Recall, that R is the set of all real numbers, Z is the set of all integers. (a) ƒ: R → R, f(x) = 9. (b) f: Z→R, f(x) = √x² +3. (c) f: RR, f(x) = √√x+5. (d) f: Z→R, f(x) = ±x². (e) ƒ: R→ Z, ƒ(x) = [x]. Note that f is the ceiling function.

Fig: 1