8. They have breakfast before ......... for school . ( leave )

9. They stopped ..... volleyball because of the heavy rain ( play )

10. Their hobby is ..... television ( watch )

11.I prefer ...... TV to ........ books ( watch / read )

12. They suggested ......... the Revolutionary museum . ( visit)

Verb froms 

1. Would you mind ......... yourr dictionary ? ( lend )

2. What about ......... to the library now ? ( go ) 

3 . She enjoyed .... when she was a young girl . ( read )

4. After ..... their homework , they watched thier farvorite program ( do )

5. They are very interested in .... stamps ( collect )

6. She is very good at ...... English ( speak )

7. She dislikes ............ early on Sunday ( get up )

Question words before To infinitive 

1. have you decided ..... to cook for dinner this evening ? ( who / whom / what / why )

2. She didn't know ....... or stay ( to go /whether to go / if to go / if that she go )

3. Have you decided what place ........ on your next holiday ? ( visit / will visit / to visit / you visted )

4. Can you tell me how to .... this washing machine ? ( to operate / I could operate / operating / could I operate )

5. They đin't know .... during their holiday ( whether to do / how to do / what to do / why to do )

Indirect questions with If / Whether 

1. Bill .... the teacher whether he could red the poem ( told / said to / asked / wanted )

2. Christ wanted to know if her mother ..... at the meeting . ( will be / can be / would be / may be )

3. Kathy asked me if I ...... go out at 3 o'clock ( could / can / will / may )

4. The shop assistant asked me ... .. those shoes were tô small for me ( that / if / whether / b and c )

5. The wanted to know if they ...... go to school the next Sunday ( must / had / could / will )

65 giờ : 4 - 10 giờ 20 phút  = 16,25 - 10 giờ 20 phút = 5,91 giờ

20,453 + 84,02 x 0,95 = 100,272

Tóm tắt 

Nhôm                                           Nước

m₁ = 3 kg                                     t₁ = 20^oC

t₁ = 122^oC                                    t₂ = 22^oC

t₂ = 22^oC                                      c₂ = 4200 J/kg.K

c₁ = 880 J/kg.K                             m₂ = ?

Giải

Nhiệt lượng của quả cầu nhôm tỏa ra là

\(Q_{tỏa}=m_1.c_1.\left(t_1-t_2\right)=3.880.\left(122-22\right)=264000\left(J\right)\)

Ta có Q_thu = Q_tỏa

\(\Rightarrow m_2.c_2.\left(t_2-t_1\right)=26400\left(J\right)\\ \Rightarrow m_2=\dfrac{26400:\left(22-20\right)}{4200}\approx3,14\left(kg\right)\)

\(\left(x+5\right)\left(3x-7\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x+5=0\\3x-7=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-5\\x=\dfrac{7}{3}\end{matrix}\right.\)