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1,Sarah is younger than Tim

2, Your house is smaller than our house

3, Bill is shorter than David

4, My marks is better than Jack's marks

5, That book is as expensive as this book

6, My bike is faster than your bike

I. Rewrite each sentence so it has the same meaning. Use a comparative form of the adjective in brackets.

1. Tim is older than Sarah ( young)

Sarah .......is younger than Tim..........................................................

2. Our house is larger than yours ( small)

Your house is ..............smaller than our house........................................

3. Bill is not as tall as David (short)

Bill is .....................shorter than David.............................................

4. Jack's marks are worse than mine (good)

My marks ....................are better than Jack's marks.......................................

5. This book is the same price at that one (expensive)

That book ................is as expensive as this one............................................

6. Your bike is slower than mine (fast)

My bike ....................is faster than yours ...........................................

Choose the more appropriate words

1.Of the four dresses, I like the red one(better/best)

2. Bill is the (happier/happiest) person we know.

3. Pat’s cat is (faster/fastest) than Peter’s.

4.This poster is (colourfuler/more colourful) than the one in the hall.

5.Does Fred feel ( weller/better) today than he did yesterday?

6.This vegetable soup tastes very( good/best)

7.Jane is the ( less/least) athletic of all the women.

8. My cat is the ( prettier/ prettiest) of the two.

9.This summary is ( the better/ the best) of the pair.

10. The colder the weather gets,(sicker/the sicker) I feel.

Choose the more appropriate words

1.Of the four dresses, I like the red one(better/best)

2. Bill is the (happier/happiest) person we know.

3. Pat’s cat is (faster/fastest) than Peter’s.

4.This poster is (colourfuler/more colourful) than the one in the hall.

5.Does Fred feel ( weller/better) today than he did yesterday?

6.This vegetable soup tastes very( good/best)

7.Jane is the ( less/least) athletic of all the women.

8. My cat is the ( prettier/ prettiest) of the two.

9.This summary is ( the better/ the best) of the pair.

10. The colder the weather gets,(sicker/the sicker) I feel.

10. Did she (buy).................buy.............. a new ruler yesterday?
11. Did he ( talk)................talk................. with his parents about his vacation in Da Lat since last year.?
12. Was Lan and Hoa (be) your school two years ago?
13. What did they (play) ................play.............last week?
14. What have the student (wear)....................worn.................. at school for two years?
15. Where did you (put) ...........put......... the cake every day?
16. Is he (visit) ...................visiting................a lot of friends in Ho Chi Minh city at the moment?
17. Did his uncle (take)...............take..............him to see Tri Nguyen aquarium until present?
18. Did Liz (buy)..............buy............. a lot of souvenirs yesterday?
19. Did they (put) ..............put.............the fish in the big bag since last Sunday?
20. Was Tam (be) at home last night? – Yes, he ...........was.........be).
21. I _______haven't seen______ your brother recently (not/see)
22. John _______has just finished______ his assignment (just/finish)
24. We (visit ) _______are visiting______the museum at the moment.
25. My children (be)____are_____tairs now. They (play)_____are playing______ games.
26. Listen! The teacher ( explain) _______is explaining_______a new lesson to us.
27. At present, the social networks ________is becoming______ (become) more popular among young generation.
28. I _______haven't listened_______ (not listen) to their new CD yet. Is it any good?
29. When I was a student, I ________didn't like_______ (not like) doing homework.
30. Facebook _______was founded_______ (found) in 2004 by Mark Zuckerberg and Eduardo Saverin.
31. The American _______spends_______ (spend) 34 hours a week watching television.
32. _______Have you ever made_______ (you/ ever/ make) origami cranes?
33. Do you adore ________lying______ (lie) in a hot bath?
34. Please try _______to arrive_______ (arrive) punctually at 8.30.
35 Many teenagers prefer _______watching_______ (watch) TV to _______reading_______ (read) books
Complete the sentences with the correct form of the words in brackets.
1. Some people think that health is _______more important______ than money. (important)
2. The pollution in our city is much _______worse______ than it used to be. (bad)
3. My new teacher explained the lessons _______more clearly______ than my old teacher. (clearly)
4. He doesn’t play volleyball as _______well______ as his brother. (good)
5. Get rid of the sorrow! You will do it _______better______ next time. (good)
6. Communication is a lot _______easier______ than it was 50 years ago. (easy)
7. People in rural areas wear _______more simply______ than those in cities. (simply)
8. Robert arrived at the meeting _______more lately______ than Francis. (lately)
9. These trousers are too wide. Do you have any that are ______narrower/more narrow_______? (narrow)
10. My mother always gets up _______earlier______ than everybody else in the house. (early)
11. Rene speaks ______more fluently_______ than the other ESL students in the class. (fluently)
12. Can’t you think of anything _______more intelligent______ to say? (intelligent)
13. I think his new book is much _______more boring______ than his last one. (boring)
14. Max finished the homework _______faster______ than anyone else in the class. (fast)
15. He doesn’t look as _______happy______ as he used to. (happy)

\(A=x^2-4x+1\)

\(\Rightarrow A=x^2-4x+4-3\)

\(\Rightarrow A=\left(x-2\right)^2-3\)

Do \(\left(x-2\right)^2\ge0\) với \(\forall x\) (dấu "=" xảy ra \(\Leftrightarrow x-2=0\Rightarrow x=2\))

\(\Rightarrow\left(x-2\right)^2-3\ge-3\) hay \(A\ge-3\) (dấu "=" xảy ra \(\Leftrightarrow x=2\))

Vậy \(A_{min}=-3\) tại \(x=2\)

\(B=4x^2+4x+11\)

\(\Rightarrow B=\left(2x\right)^2+4x+1^2+10\)

\(\Rightarrow B=\left(2x+1\right)^2+10\)

Do \(\left(2x+1\right)^2\ge0\) với \(\forall x\) (dấu "=" xảy ra \(\Leftrightarrow2x+1=0\Rightarrow2x=1\Rightarrow x=\dfrac{1}{2}\))

\(\Rightarrow\left(2x+1\right)^2+10\ge10\) hay \(B\ge10\) (dấu ''='' xảy ra \(\Leftrightarrow x=\dfrac{1}{2}\))

Vậy \(B_{min}=10\) tại \(x=\dfrac{1}{2}\)

Chúc Bạn Học Tốt!!!

\(A=x^2-4x+1=x^2-4x+4-3=\left(x-2\right)^2-3\ge-3\forall x\)

Dấu " = " xảy ra

\(\Leftrightarrow\left(x-2\right)^2=0\Leftrightarrow x-2=0\Leftrightarrow x=2\)

Vậy Min A là : \(-3\Leftrightarrow x=2\)

\(B=4x^2+4x+11=\left(2x\right)^2+2.2x+1+10=\left(2x+1\right)^2+10\ge10\forall x\)Dấu " = " xảy ra

\(\Leftrightarrow\left(2x+1\right)^2=0\Leftrightarrow2x+1=0\Leftrightarrow2x=-1\Leftrightarrow x=-\dfrac{1}{2}\)

Vậy Min B là : \(11\Leftrightarrow x=-\dfrac{1}{2}\)

1) m dd naOH (bđ) = \(250.1,2=300\left(g\right)\)

\(m_{NaOH\left(bđ\right)}=\frac{300.10}{200}=30\left(g\right)\)

\(n_{Na}=\frac{m}{23}\left(mol\right)\)

PTHH: \(2Na+2H_2O\rightarrow2NaOH+H_2\uparrow\)

_______ \(\frac{m}{23}\) -------------------> \(\frac{m}{23}\)-------> \(\frac{m}{46}\)(mol)

\(=>m_{NaOH}=\frac{m}{23}.40=\frac{40m}{23}\left(g\right)\)

=> \(m_{dd}\) sau pư = \(m+300-2.\frac{m}{46}\) = \(\frac{22m}{23}+300\left(g\right)\)

=> \(C\%=\frac{\frac{40m}{23}}{\frac{22m}{23}+300}.100\%=14,94\%\)

=> m = 28,1 (g)

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https://hoc24.vn/hoi-dap/question/132202.html

Change the sentences into the passive voice

1. My teacher will make a report about the environment next week.

=> A report about the environment will be made by my teacher next week.

2. How will you develop alternative sources of energy in the near future?

=> How will alternative sources of energy be developed by you in the near future?

3. Will people reduce the consumption of natural gas and use wind energy instead?

=> Will the consumption of natural gas be reduced and wind energy be used instead?

4. They built the Temple of Literature under Emperor Ly Nhan Tong in 1076.

=> The Temple of Literature under Emperor Ly Nhan Tong was built on 1076.

5. People consider Harvard University as the best university in the world.

=> Harvard University is considered as the best university in the world.

6. They grow many flowers along two sides of the road.
=> Many flowers are grown along two sides of the road.

1. My friends ______ a great time in Nha Trang last year. (have)
(-)…………didn't have....……….
(?)…………Did your friends have a great time in Nha Trang last year……….?
2. They (buy ) ……………. that house last year.
(-)................didn't buy................
(?)…………Did they buy that house last year…………?
3. She (not go) …………didn't............... to school yesterday.
4. She (spend) ____ all her money since last week.
(-)…………hasn't spent…………
(?)…………Has she spent all her money since last week………..?
5- He (be).................................. a doctor two years ago.
(-)…………wasn't……..
(?)…………Was he a doctor two years ago.....………?
6- My parents (not be) .............hasn't been..........teachers for two years.
7- He ( not be) ..............didn't be............a mechanic last Monday.
8. Ba (wear)............................. the cap all day yesterday.
(-)…………didn't wear…………
(?)…………Did Ba wear the cap all day yesterday.……….?
9. I (eat) ..........................a lot of fish every morning
(-)……………don't eat…………….
(?)……………Do you eat many fishes every morning…………...?

=> Câu này có vấn đề???

a/ \(\sqrt{x^2-2x+1}=5\)

\(\Leftrightarrow\sqrt{\left(x-1\right)^2}=5\)

\(\Leftrightarrow\left(x-1\right)^2=25\)

\(\Leftrightarrow\left(x-1\right)^2-25=0\)

\(\Leftrightarrow\left(x-1-5\right)\left(x-1+5\right)=0\)

\(\Leftrightarrow\left(x-6\right)\left(x+4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-6=0\\x+4=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)

Vậy...

b/ \(\sqrt{x^2+x+1}=1\)

\(\Leftrightarrow x^2+x+1=1\)

\(\Leftrightarrow x^2+x+1-1=0\)

\(\Leftrightarrow x\left(x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)

Vậy....

c/ ĐKXĐ : \(x\ge-2\)

Ta có :

\(\sqrt{x+2}=5\)

\(\Leftrightarrow x+2=25\)

\(\Leftrightarrow x=23\)

Vậy...

d/ \(\sqrt{x^2+1}=3\)

\(\Leftrightarrow x^2+1=9\)

\(\Leftrightarrow x^2+1-9=0\)

\(\Leftrightarrow x^2-8=0\)

\(\Leftrightarrow\left(x-2\sqrt{2}\right)\left(x+2\sqrt{2}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2\sqrt{2}\\x=-2\sqrt{2}\end{matrix}\right.\)

Vậy....

e/ ĐKXĐ : \(x\ge1\)

\(3-\sqrt{x-1}=9\)

\(\sqrt{x-1}=-6\) (vô lí)

Vậy...

f/ ĐKXĐ : \(x\ge-5\)

Ta có :

\(\sqrt{x+5}=-2\) (vô lí)

Vậy....

g/ ĐKXĐ : \(x\ge1\)

Ta có :

\(3\sqrt{x-1}=9\)

\(\Leftrightarrow\sqrt{x-1}=3\)

\(\Leftrightarrow x-1=9\)

\(\Leftrightarrow x=10\)

Vậy..

1) \(A=x^2-4x+1\)

\(A=x^2-4x+4-3\)

\(A=\left(x^2-4x+4\right)-3\)

\(A=\left(x-2\right)^2-3\)

Ta có: \(\left(x-2\right)^2\ge0\) với mọi x

\(\Rightarrow\left(x-2\right)^2-3\ge-3\) với mọi x

Vậy MIinA = -3 khi x = 2

2) \(B=-x^2+13x+2012\)

\(B=-x^2+13x-\frac{169}{4}+\frac{169}{4}+2012\)

\(B=-\left(x^2-13+\frac{169}{4}\right)+\left(\frac{169}{4}+2012\right)\)

\(B=-\left(x-\frac{13}{2}\right)^2+\frac{8217}{4}\)

Ta có: \(\left(x-\frac{13}{2}\right)^2\ge0\) với mọi x

\(-\left(x-\frac{13}{2}\right)^2\le0\) với mọi x

\(\Rightarrow-\left(x-\frac{13}{2}\right)^2+\frac{8217}{4}\le\frac{8217}{4}\)

Vây \(Max\left(B\right)=\frac{8217}{4}\) khi \(x=\frac{13}{2}\)

pthh :\(2A + 2H_20 \rightarrow 2AOH + H_2 \)

\(B+2H_2O \rightarrow B(OH)_2+H_2\)

\(n_{H_2}=\frac{4,48}{22,4}=0,2 (mol)\)

Ta thấy :

\(\sum n_{OH}=0,5.n_{H_2}\)

Mà \(n_{H_2}=0,2 (mol)\) \(\rightarrow \sum n_{OH}=0,1 (mol)\)

\(m_E=m_A+m_B+m_{OH}=21,5+0,1.17=23,2 (g)\)

b) Vì thể tích khí oxi tác dụng với kim loại A = lượng thể tích oxi tác dụng với kim loại B mà tỷ lệ thể tích bằng tỷ lệ số mol

Suy ra : số mol khí oxi tác dụng với kim loại A = số mol oxi tác dụng với kim loại B ( trong 21,5 g ) (1)

PTHH : \(4A+O_2->2A_2O\)

\(2B+O_2->2BO\)

Gọi số mol của A, B lần lượt là a, b

Từ (1) \(\rightarrow 0,25a=0,5b\) (*)

Vì khối lượng kim loại bằng 21,5 gam \(\rightarrow\)\(aA+bB=21,5 (g)\) (***)

Từ câu a, tác dụng với nước thu được 0,2 mol khí hidro \(\rightarrow 0,5a+b=0,2\) (**)

Giải phương trình (*)(**) : \(a=0,2 ; b=0,1\)

Thay vào (***) : \(0,2A+0,1B=21,5\)

Vì A và B > 0 \(\rightarrow A<\frac{21,5}{0,2}=107,5\)

Ta thử các trường hợp của A tương ứng với B

Vậy A là Kali và B là Bari