I was told the film would be very good (led) `->` .......... You don't have to buy one if you don't like it (obligation) `->` ....................

`->` I was led to believe the film would be very good. 

`-` Chủ động: lead sb to believe sth (khiến ai tin tưởng) 

`->` Bị động: sb tobe led to believe sth (ai tin tưởng rằng...) 

`=>` You aren't under obligation to buy one if you don't like it.

`-` "Don't have" `->` Chia thì HTD `->` tobe "am/is/are"

`( - )` S + am/is/are + not + N/adj/... + O

`-` Cấu trúc: be under obligation to do sth = have to do sth: phải làm gì (có việc phải làm)