used to do的否定形式是didn't use to do 或 usedn't to do;疑问形式是Did you use to do sth?
例句:My brother used to go swimming in the sea.我哥哥过去常常在海里游泳。否定形式是My brotherdidn't use to go swimming in the sea.
疑问形式是Did your brother use to go swimming in the sea?
be used to doing的例句:I am used to having a cup of tea in the morning.
我习惯于早上喝一杯茶。