1.i have never been to such a beautiful country before

-> this is the first......

2. when did she start studying at this school?

-> how long ago...

-> how long is it since....

-> how long...

3. the last time i played tennis was 6 months ago

-> i have...

-> i last...

4. we last saw our grandparents 2 years ago

-> we haven't...

-> it's

5.how long have you been teaching at this school?

-> when...

-> how long ago...

-> how long...

Các công thức đổi HTHT - QKĐ

Structure 1: 

S + has/have + not + V3/ed + for/since + time 

--> S + last + V2/ed 

--> The last time + S+ V2/ed + was + time 

--> It is / has been + time + since + S+ (last) + V2/ed 

Structure 2: 

How long + has/have + S+ V3/ed?

--> When + did + S + V1?

--> How long is it + since + S+ V2/ed ?

Structure 3:

S + has/have + V3/ed + for/since + time 

--> S + started / began + to V / Ving 

--> It is / has been + time + since + S+ V2/ed 

Structure 4: 

S + has/have + not/never + V3/ed + ... before

--> This/It is the first time + S+ has/have+ V3/ed

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1. This is the first time I have been to such a beautiful country.

2. 

- How long ago did she start studying at this school?

- How long is it since she started studying at this school?

- How long has she been studying at this school?

3. 

- I have not played tennis for 6 months.

- I last played tennis 6 months ago.

4.

- We haven't seen our grandparents for 2 years.

- It's 2 years since we last saw our grandparents. 

5. 

- When did you start teaching at this school?

- How long ago did you start teaching at this school?

- How long is it since you started teaching at this school?

`1` This is the first time I have been to such a beautiful country.

`-` S + have/has + not/never + V3/ed + before: Chưa từng làm gì trước kia.

`=` This is the first time + S + have/has + (ever) + V3/ed: Lần đầu tiên ai làm gì.

`2`

`-` How long ago did she start studying at this school?

`-` How long is it since she started studying at this school?

`-` How long has she studied at this school?

`->` When did + S + start/begin + to V/Ving?: Bắt đầu làm gì từ khi nào?

`=` How long ago did + S + V?: Bắt đầu làm gì từ khi nào?

`=` How long is it since + S + started/began + to V/Ving?: Đã bao lâu kể từ khi ai bắt đầu làm gì?

`=` How long + have/has + S + V3/ed?: Đã làm gì trong bao lâu?

`3`

`-` I have not played tennis for `6` months.

`-` I last played tennis `6` months ago.

`->` The last time + S + V2/ed + was + khoảng thời gian + ago: Lần cuối làm gì là từ khi nào.

`=` S + last + V2/ed + khoảng thời gian + ago: Lần cuối làm gì là từ khi nào.

`=` S + have/has + not + V3/ed + for + khoảng thời gian: Đã không làm gì trong bao lâu.

`4`

`-` We haven’t seen our grandparents for `2` years.

`-` It’s `2` years since we (last) saw our grandparents.

`->` S + last + V2/ed + khoảng thời gian + ago: Lần cuối làm gì là từ khi nào.

`=` S + have/has + not + V3/ed + for + khoảng thời gian: Đã không làm gì trong bao lâu.

`=` It’s + khoảng thời gian + since + S + (last) + V2/ed: Đã bao lâu kể từ khi ai lần cuối làm gì.

`5`

`-` When did you start teaching at this school?

`-` How long ago did you start teaching at this school?

`-` How long have you taught at this school?

`->` When did + S + start/begin + to V/Ving?: Bắt đầu làm gì từ khi nào?

`=` How long ago did + S + V?: Bắt đầu làm gì từ khi nào?

`=` How long + have/has + S + V3/ed?: Đã làm gì được bao lâu?