1. Lan didn't buy a new dress yesterday

2. They weren't late for school

3. Mr.Ben didn't take his children to the zoo last Sunday

4. Mai didn't make a mistake in her exam

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Công thức thì QKĐ

- Với tobe

(+) S + tobe(was/were) + adj/N

(-) S + tobe(was/were) + not + adj/N

- Với động từ

(+) S + V2/ed + ....

(-) S + didn't + Vinf

1. Lan didn't buy a new dress yesterday.

2. They weren't late for school.

3. Mr. Ben didn't take his children to the zoo last Sunday.

4. Mai didn't make a mistake in her exam.

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Note: Thì QKĐ:

- Với động từ thường:

(+) S + Ved/2...

(-) S + didn't + V-inf...

(?) Did + S + V-inf...?

- Với tobe:

(+) S + was/were...

(-) S + wasn't/weren't...

(?) Was/were + S...?