Bột canxicacbonat tan trong dung dịch nào sau đây :

A.HCl                        B.NaOH                 C.KNO₃     D.NaCl

a, Vì 2013 là số lẻ nên (\(^{1^{2013}+2^{2013}+...n^{2013}}\))⋮(1+2+...+n)

=>\(\left(1^{2013}+2^{2013}+...+n^{2013}\right)\)⋮\(\dfrac{n\left(n+1\right)}{2}\)

=>\(2\left(1^{2013}+2^{2013}+...+n^{2003}\right)\)⋮n(n+1)

đpcm

Câu 1.Sắt II clorua có CTHH là:

a.FeCl₃                   b.FeBr₂                              c.FeCl₂                 d.FeBr₃

yes bị tụi rank :)) ko hỉu tại sao luôn :)

Cho e hỏi cái từ đầu cấp bậc của e là thượng sĩ sao tự nhiện lại nhảy tót xuống tận trung sĩ vậy ?

ủa là sao ? ai giải thik cho e với :((( 

Mark the letter A, B, C or D to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions.

1.   A. bucket                    B. underline                       C. multiple                  D. sugar

2.   A. inside                     B. provide                          C. since                       D. sight          

Mark the letter A, B, C or D to indicate the word that differs from the other three in the position of primary stress in each of the following questions.

3.   A. annoyed                 B. sculpture                       C. complex                  D. starter        

4.   A. profession              B. bilingual                 C. attendance                     D. exotic

Mark the letter A, B, C or D to indicate the correct answer to each of the following question.

5. I wish you__________your clothes all over the floor.

A. don't leave                   B. wouldn't leave        C. won't leave          D. not leave

6. I wasn't too keen on________to the party.

A. go                                   B.goes                           C. going            D. to go

7.   She went to the bookshop_________she wanted to buy a comic book.

A. although                        B. because                       C.despite                      D. because of

8.   Students have___________or no choice in the matter.

A. a few                              B. a little             C. few                        D. little

9.   Students___________study hard will do well in my class.

A. who                               B. whose              C. which                      D. whom

10. He has been __________for ten jobs so far.

A. turned down                  B. turned up                    C.  let in                      D. let out

11. Have you ordered the wedding __________yet?

A.  invite                             B. invitation                    C. invitations  D. invited

12. The Great Walls of China __________ thousands of years ago.

A. is built                         B. was built                        C. is building  D. was building

13. _________ you study for these exams, _________ you will do.

A. The harder / the better                              B. The more / the much

C. The hardest / the best                               D. The more hard / the more good

III/ WRITING:  Rewrite the sentences beginning with the phrases given. 

     1.   What a pity you can’t stay here with us. 

I wish ……………………………………………………………………………………

     2.   I’m sorry he doesn’t win the first prize. 

I wish ……………………………………………………………………………………

     3.   We don’t have time to help you. 

We wish  …………………………………………………………………………………

     4.   They canceled the flight because  there was a snow storm. 

There was a snow storm …………………………………………………………………

     5.   He didn’t study hard so he failed the exam. 

He failed the exam…………………………………………………………………………

     6.  It’s a pity my father can’t speak English

I wish………………………………………………………………………………………

     7. I’m sorry I can’t speak English perfectly.   

I wish ……………………………………………………………………………………

     8. The test was very long. I couldn’t finish it in an hour

The test was so ……………………………………………………………………………

4)  I often play soccer …………………..weekends. 

    a/ on                          b/ in                              c/ about                  d/ at 

5)  Hoa worked hard, …………………she passed the exam. 

    a/ because                     b/ so                              c/ if                     d/ however 

6)  Nam wishes his father…………………………………here to help him now. 

    a/ is                          b/ were                            c/ will be                d/ was 

7)  Lan can’t swim fast. She wishes she…………………………..faster. 

    a/ can swim              b/ couldn’t swim                   c/ could swim             d/ can’t swim 

8)  Lan wishes she ………………………………..have to clean all the windows. 

    a/ don’t                       b/ doesn’t                         c/ wasn’t                 d/ didn’t 

9)  I wish I ………………………………get good marks for the coming exam. 

    a/ can                         b/ could                           c/ should                 d/ will 

10) I have studied English…………………………………………more than three years. 

    a/ for                         b/ in                              c/ since                  d/ at 

2/ Supply the correct verb form 

1)  ……………….you…………………. ( go )out last night? 

2)  ………. you………………………from George recently? ( hear ) 

3)  It’s the first time he ……………………..a car. ( drive ) 

4)  Everything is going well. We…………………….any problems so far.( not have ) 

5)  I wish I …………………..you someday. ( visit) 

III/ WRITING:  Rewrite the sentences beginning with the phrases given. 

     1.   What a pity you can’t stay here with us. 

I wish ……………………………………………………………………………………

     2.   I’m sorry he doesn’t win the first prize. 

I wish ……………………………………………………………………………………

     3.   We don’t have time to help you. 

We wish  …………………………………………………………………………………

     4.   They canceled the flight because  there was a snow storm. 

There was a snow storm …………………………………………………………………

     5.   He didn’t study hard so he failed the exam. 

He failed the exam…………………………………………………………………………

     6.  It’s a pity my father can’t speak English

I wish………………………………………………………………………………………

     7. I’m sorry I can’t speak English perfectly.   

I wish ……………………………………………………………………………………

     8. The test was very long. I couldn’t finish it in an hour

The test was so ……………………………………………………………………………

Có