1 A=> don't

2 C => as

3 B => hard

4 D => easily

5 D => perfect

1 A => ought to

2 A => to leave

3 A => is

4 C => up

5 B => upstairs 

1: A: ought => ought to

2: A: leave => to leave

3: A: are => is

4: C: on => up

5: B: upstairs => upstairs 

1 C => is living

2 C => closed

3 B => like

4 B => out

5 C => fool

11 D => bỏ

12 C => which

13 B => to which

14 A => who

15 B => where

16 C => will join in

17 D => at

18 D => with

19 D => bad for

20 B => of

21 A => for

1 D => on

2 A => betweem

3 B => so

4 B => knew

5 B => because

a,c đúng còn b em hiểu sai đề

\(\left(21x^3y^4+7x^2y^3-14x^4y^3\right):7x^2y^3=\dfrac{21x^3y^4+7x^2y^3-14x^4y^3}{7x^2y^3}\) mới đúng

\(=\dfrac{7x^2y^3\left(3xy+1-2x^2\right)}{7x^2y^3}=-2x^2+3xy+1\)

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