\(a,\Leftrightarrow-a=2\Leftrightarrow a=-2\Leftrightarrow y=-2x\\ b,y=-8\Leftrightarrow x=-\dfrac{8}{-2}=4\)

Đặt \(n_{MgO}=x(mol);n_{FeO}=y(mol)\)

\(\Rightarrow 40x+72y=4,88(1)\\ MgO+H_2SO_4\to MgSO_4+H_2O\\ FeO+H_2SO_4\to FeSO_4+H_2O\\\Rightarrow x+y=\dfrac{8,82}{98}=0,09(2)\\ (1)(2)\Rightarrow x=0,05(mol);y=0,04(mol)\\ \Rightarrow \%_{MgO}=\dfrac{0,05.40}{4,88}.100\%=40,98\%\)

Câu 7:

\(CTHH:XO_2\\ n_{XO_2}=\dfrac{0,6.10^{23}}{6.10^{23}}=0,1(mol)\\ \Rightarrow M_{XO_2}=\dfrac{4,4}{0,1}=44(g/mol)\\ \Rightarrow M_X=44-16.2=12(g/mol)(C)\\ \Rightarrow CTHH:CO_2\)

Chọn B

Câu 8:

\(2Fe(OH)_3\xrightarrow{t^o}Fe_2O_3+3H_2O\)

\(\Rightarrow \text{Số phân tử }Fe(OH)_3=\dfrac{2}{3}=0,67\text{ lần số phân tử }H_2O\)

Chọn C

\(=x\left(x^2-1\right)+3\left(x^2-1\right)=\left(x+3\right)\left(x^2-1\right)=\left(x+3\right)\left(x-1\right)\left(x+1\right)\)

Bài I

\(1,=x\left(x-y\right)\\ 2,=x\left(y+1\right)+y+1=\left(x+1\right)\left(y+1\right)\\ 3,=x\left(x^2-2x-5x+10\right)=x\left(x-2\right)\left(x-5\right)\)

Bài II

\(1,=x-x^2+x^2-x-2=-2\\ 2,\Leftrightarrow x^2+6x+9-x^2=45\\ \Leftrightarrow6x=36\Leftrightarrow x=6\)

Bài III

\(1,A=\dfrac{4-9}{3\left(2+5\right)}=\dfrac{-5}{3\cdot7}=-\dfrac{5}{21}\\ 2,B=\dfrac{x^2-3x+2x^2+6x-3x^2-9}{\left(x-3\right)\left(x+3\right)}=\dfrac{3\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{3}{x+3}\\ 3,P=AB=\dfrac{\left(x-3\right)\left(x+3\right)}{3\left(x+5\right)}\cdot\dfrac{3}{x+3}=\dfrac{x-3}{x+5}=1-\dfrac{8}{x+5}\in Z\\ \Leftrightarrow x+5\inƯ\left(8\right)=\left\{-8;-4;-2;-1;1;2;4;8\right\}\\ \Leftrightarrow x\in\left\{-13;-9;-7;-6;-4;-1;3\right\}\)

Choose the letter A, B, C or D to complete the sentences

Question 1. Look! He ________ football now.

A. is playing              B. plays                      C. played                          D. was playing

Question 2. It’s very ________ of you to help me.

A. talkative               B. active                    C. nice                                D. confident

Question 3. Nam and Ba ________ ice cream at the moment.

A. eating                    B. is eating                C. was eating                         D. are eating

Question 4. Steve can deal with difficult exercises. He’s a __________ boy.

A. creative                 B. intelligent             C. sporty                           D. kind

Question 5. Please be ___________ when you have to use fire to cook.

A. handsome             B. clever                    C. careful                         D. reliable

Question 6. She is so ___________ that she doesn’t talk much to strangers.

A. reserved                B. clever                    C. active                           D. smart

Question 7. The part between the head and the body is the _________.

A. leg                          B. neck                       C. knee                            D. shoulder

Question 8. My friend, Lan is a ________ student. She always finishes homework on time.

A. hard-working       B. confident                 C. shy                               D. reliable

Question 9. What does your best friend look like?

A. He is funny          B. He is kind             C. He is clever                      D. He is handsome

Question 10. What’s your classmate like?

A. She’s patient        B. She’s beautiful        C. She’s tall                     D. She’s thin

Question 11. Peter __________ a straight nose and fair skin.

A. goes                       B. comes                    C. does                                   D. has

Question 12. Would you like _________ to the hospital to visit my mother?

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

Question 13. _______ you _______ an English class tomorrow?

A. Do – have             B. Are – having        C. Will – having                   D. Is – have

Question 14. That girl has yellow hair. She has _______ hair.

A. black                     B. wavy                      C. blonde                               D. curly

Question 15. We should brush our ____________ twice a day.

A. feet                        B. teeth                      C. hair                                    D. toe

em có thấy giống bài thi đâu ạ ?

Both - and

VI. Choose the word or phrase (A,B,C or D) that best fits the space in each sentence meaningfully.

23. Hue beef noodle is really  ______. I like it a lot.

A.awful                                   B.salty                         C.delicious                  D.bitter

24. They are going to break eggs to make ______ for breakfast.

A.omelet                                 B.noodle                     C.tofu                          D.spaghetti

25. Most of us listen to ______for pleasure.

A.music                                   B.films                        C.paintings                  D.puppet

26. There is a new ______of handmade flowers at this city gallery.

A.party                                    B.exhibition                C.show                        D.tour

27. Paul thinks making ______is an interesting hobby.

A. gymnastics                         B.pottery                     C.skating                     D.bottles

28. ______in Vietnam is unique because it is performed in a pool.

A.Folk music                           B.Dong Ho paintings  C.Folk dance               D.Water puppetry

VII. Rearrange the words or phrases to make complete sentences.

29. Do/ holiday/ camping/ summer/ go/ children/ your/ every/ ?

  ________________________________________________________________?

A.Do your children camping go summer every holiday?

B.Do your children go camping every summer holiday?

C.Do every summer your children go camping holiday?

D.Do every holiday children go camping your summer?

30.Rubbish/ full/ it/ decided/ they/ to / last Sunday/ lake/ the/ was/ of / so/ clean/ up/ .

 The lake  _____________________________________________________________________________

A.The lake was full of rubbish so they decided to clean it up last Sunday.

B.The lake was rubbish of full so they decided clean it up to last Sunday.

C.The lake they decided to clean up it rubbish was so full of last Sunday.

D.The lake they clean rubbish up so it was decided to full of last Sunday.

VIII. Choose the most correct answer from the following questions 

31. What will you do on the Tet holiday?

A.I will go to school to study.

B.I will go to the hospital.

C.I will visit my grandparents and travel with my family.

D.I will go there by car.

32. What do you usually buy on the Tet holiday?

A.I usually buy new clothes.

B.I usually buy lucky money.

C.I buy usually new clothes.

D.I buy usually lucky money.

33. What is your hobby?

A.I like playing board games.

B.I like taking photos.

C.I like playing the piano.

D.All of them

34. Do you like studying abroad or studying in your country?

A.Yes, I do.

B.No, I don’t.

C.I like studying abroad.

D.I like studying abroad and studying in my country.

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