$1.$ I lived on a farm once, but I don’t any more
I used to live on a farm once.

S + V(quá khứ), but S + not + V.

$→$ S + used to + V.
$2.$ My father gave up smoking two years ago
My father used to smoke two years ago.

S + gave up + V_ing.

$→$ S + used to + V.
$4.$ My sister played tennis a lot, but she doesn’t play very often now
My sister used to play tennis a lot.

S + V(quá khứ), but S + not + V.

$→$ S + used to + V.

$5.$ She  no longer  takes a taxi  to her office.
I used to take a taxi to her office.

S + no longer + V(hiện tại).

$→$ S + used to + V.

`\color{cyan}{\text{@Bulletproof Boy Scout}}`

$1.$ I used to live on a farm.

$2.$ My father used to smoke two years ago.

$4.$ My sister used to play tennis a lot.

$5.$ I used to take a taxi to her office.

Công thức:

Khẳng định (+): S + used to + V

Phủ định (-): S + did not + use to + V

Nghi vấn (?): Did + S + use to + V?

$Chúc$ $bạn$ $học$ $tốt$