please sir fast its very urgent

5. Let { an be a sequence. (a) Prove that limn toan = L if and only if lim, . (an - L) = 0. (b) Prove that lim, +0 an = 0 if and only if lim, +. an) = 0. (c) Prove that if limn-+0% an = L, then lim, . an = L