You have to move a heavy table. You want joe to give you a hand with it. Ask him.
Joe, you couldn't give me a hand (with this table) , could you?
You need a bicycle pump. Perhaps Helen has got one. Ask her.
Helen, you haven't got a bicycle pump, have you? or ... you don't have a bicycle pump, do you?
Ann has a car and you need a lift to the station. Perhaps she'll take you. Ask her.
Ann, you couldn't take me to the station, could you? or ... you couldn't give me a lift to the station, could you?
You're looking for your keys. Perhaps Robert has seen them. Ask him.
Robert, you haven't seen my keys, have you?
You need a pen. Perhaps Jane has got one. Ask her
Jane, you haven't got a pen, have you?
You're looking for Sarah. Perhaps Kate knows where she is. Ask her.
Kate, you don't know where Sarah is, do you? or ... you haven't seen Sarah, have you?