` 1 `. I lived on a farm once, but I don’t any more.
` ⇒ ` I used to live on a farm.
` 2 `. I usually watched football every Sunday last year.
` ⇒ ` I used to watching football every Sunday.
` 3 `. There was a lake behind my parents’ house.
` ⇒ ` There is used to be a lake behind my parents' house.
` 4 `. I usually stayed up late to watch football matches last year.
` ⇒ ` I used to stay up late to watch football matches last year.
` 5 `. There were some trees in the field.
` ⇒ ` There used to be some trees in the field.
` 6 `. She doesn’t live with her parents any more.
` ⇒ ` She used to live with her parents.
` 7 `. I often played volley every Sunday morning last year.
` ⇒ ` I used to play volleyball every Sunday morning.
` 8 `. He is not a poor man any more.
` ⇒ ` He used to a poor man.
+ Công thức: (+): S + used to + V(inf.)
(-): S + didn’t + use to + V(inf.)
(?): Did + S + use to + V(inf.)...?
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