Ex2

1 B

2 D

3 B

4 D

5 D

Ex3

1 is singing

2 go

3 likes - like

4 are staying

5 reads

6 is running

7 listens-isn't listening

8 is your father - is - is watching

9 Do they go

10 are

11 doesn't go

12 go - go

13 am writing

14 have - go

15 have

Ex4

1 B

2 B

3 A

4 C

5 C

6 A

7 C

8 A

9 C

Ex5

1 B

2 A

3 C

Ex6

1 D

2 C

3 A

Ex7

1 friendly

2 talkative

3 independent

4 sensitive

5 creative

Ex7

0 f

1 c

2 h

3 a

4 d

1 Biên độ A = 8 cm

Tần số góc \(3\pi\) rad/s

Chu kì \(T=\dfrac{2\pi}{3\pi}=\dfrac{2}{3}\left(s\right)\)

Tần số \(f=\dfrac{1}{\dfrac{2}{3}}=\dfrac{3}{2}\)

Pha ban đầu \(\varphi=\dfrac{2\pi}{2}=\pi\)(rad)

2. \(x=8cos\left(\dfrac{2\pi}{3}\right)=-4\left(cm\right)\)

3. \(v_{max}=\omega A=3\pi.8=24\pi\)

\(a_{max}=\omega^2A=9\pi^2.8=72\pi^2\)