-잖아요 is used when the speaker wants to state a reason that the listener should also be aware of or when the speaker wants to remind the listener of a reason that he or she has apparently forgotten. It is used in only in conversation, not in written Koran. ex) A : 저 가수를 왜 좋아해요?(Why do you like that singer?) B : 노래도 잘하고 멋있잖아요.(He sings well and as you know is good looking, too.) A/V-지요? is used when the speaker wants to confirm with the listener or to obtain the listener's agreement about something already known. It means 'Isn't/Aren't...?' or 'Don't/Doesn't.. ?' in English. ex) A : 내가 벌써 40살이 되었어요. 세월 참 빠르지요? (I'm already 40 years old. Doesn't time just fly by?) B : 네, 정말 세월이 빨라요. (Yes, time really does fly by.) Hope it helps you.