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Nguyễn Thị Khánh Linh
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TN NM BloveJ
10 tháng 5 2022 lúc 21:01

lỗi

Ngân Vũ
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Thu Hằng
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santa
2 tháng 4 2022 lúc 8:29

Bài 3 :

a) nKMnO4 = 31,6/158 = 0,2 (mol)

PTHH : \(2KMnO_4-t^o->K_2MnO_4+MnO_2+O_2\)

Theo pthh : nO2 = 1/2 nKMnO4 = 0,1 (mol)

=> VO2 = 0,1.22,4 = 2,24 (l)

b) PTHH : \(2Mg+O_2-t^o->2MgO\)

Theo pthh : nMgO = 2nO2 = 0,2 (mol)

=> mMgO = 0,2.40 = 8 (g)

 

santa
2 tháng 4 2022 lúc 8:33

Bài 5 :

a) nCu = 0,2 (mol)

nO2 = 0,2 (mol)

PTHH : \(2Cu+O_2-t^o->2CuO\)

Nhận thấy : \(\dfrac{nCu}{2}< nO_2\left(\dfrac{0,2}{2}< 0,2\right)\) => Spu,Cu hết, O2 dư

Theo pthh : nCuO = nCu = 0,2 (mol)

=> mCuO = 0,2.80 = 16 (g)

b) PTHH : \(CuO+H_2-t^o->Cu+H_2O\)

Theo pthh : nH2 = nCuO = 0,2 (mol)

=> VH2 = 0,2.22,4 = 4,48 (l)

Minh_MinhK
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Phuong Trinh Nguyen
6 tháng 5 2021 lúc 20:15

Bài 5 hình 1: (tự vẽ hình nhé bạn)
a) Xét ΔABD và ΔACB ta có:
\(\widehat{BAD}\)\(\widehat{BAC}\) (góc chung)
\(\widehat{ABD}\)\(\widehat{ACB}\) (gt)
=> ΔABD ~ ΔACB (g-g)
=> \(\dfrac{AB}{AC}\) = \(\dfrac{BD}{CB}\) = \(\dfrac{AD}{AB}\) (tsđd)
b) Ta có: \(\dfrac{AB}{AC}\) = \(\dfrac{AD}{AB}\) (cm a)
=> \(AB^2\) = AD.AC
=> \(2^2\) = AD.4
=> AD = 1 (cm)
Ta có: AC = AD + DC (D thuộc AC)
      => 4   =   1   + DC
      => DC = 3 (cm)
c) Xét ΔABH và ΔADE ta có: 
   \(\widehat{AHB}\) = \(\widehat{AED}\) (=\(90^0\))
   \(\widehat{ADB}\) = \(\widehat{ABH}\) (ΔABD ~ ΔACB)
=> ΔABH ~ ΔADE
=> \(\dfrac{AB}{AD}\) = \(\dfrac{AH}{AE}\) = \(\dfrac{BH}{DE}\) (tsdd)
Ta có: \(\dfrac{S_{ABH}}{S_{ADE}}\) = \(\left(\dfrac{AB}{AD}\right)^2\)\(\left(\dfrac{2}{1}\right)^2\)= 4
=> đpcm

Phuong Trinh Nguyen
6 tháng 5 2021 lúc 20:29

Tiếp bài 5 hình 2 (tự vẽ hình)
a) Xét ΔABC vuông tại A ta có:
\(BC^2\) = \(AB^2\) + \(AC^2\)
\(BC^2\) = \(21^2\) + \(28^2\)
BC = 35 (cm)
b) Xét ΔABC và ΔHBA ta có:
\(\widehat{BAC}\) = \(\widehat{AHB}\) ( =\(90^0\))
\(\widehat{ABC}\) = \(\widehat{ABH}\) (góc chung)
=> ΔABC ~ ΔHBA (g-g)
=> \(\dfrac{AB}{BH}\) = \(\dfrac{BC}{AB}\) (tsdd)
=> \(AB^2\) = BH.BC
=> \(21^2\) = 35.BH
=> BH = 12,6 (cm)
c) Xét ΔABC ta có:
BD là đường p/g (gt)
=> \(\dfrac{AD}{DC}\) = \(\dfrac{AB}{BC}\) (t/c đường p/g)
Xét ΔABH ta có: 
BE là đường p/g (gt)
=> \(\dfrac{HE}{AE}\) = \(\dfrac{BH}{AB}\) (t/c đường p/g)
Mà: \(\dfrac{AB}{BC}\) = \(\dfrac{BH}{AB}\) (cm b)
=> đpcm
d) Ta có: \(\left\{{}\begin{matrix}\widehat{HBE}+\widehat{BEH}=90^0\\\widehat{ABD}+\widehat{ADB=90^0}\\\widehat{HBE}=\widehat{ABD}\end{matrix}\right.\)
=> \(\widehat{BEH}=\widehat{ADB}\)
Mà \(\widehat{BEH}=\widehat{AED}\) (2 góc dd)
Nên \(\widehat{ADB}=\widehat{AED}\)
=> đpcm

Phạm Mạnh Kiên
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Khinh Yên
15 tháng 7 2021 lúc 9:40

IV. Choose the best answer A, B, C, or D to complete each sentence.

1.Ms. Jones isn’t as nice …….. Ms. Smith.

A. as               B. for                          C. like                        D. to

2. The rooms in Graduate Towers are……….. Patterson Hall.

A. larger than                                    B. larger than that of

C. larger than those in                      D. larger than in

3. Although she is very popular, she is not……her sister.

A. pretty as                                        B. as pretty               

C. prettier than                                  D. most pretty than

4. Tuition at an American university runs……. Six thousand dollars a semester.

A. so high as                         B. as high to             

C. as high as                          D. as high than

5. Everyone looks much………. today than they did yesterday.

A. happy                    B. happily                  C. more happily        D. happier

6. Mr. Brown receives a …….. salary than anyone else in the company.

A. big                         B. more bigger          C. bigger                    D. the bigger

7. The Boeing 747 is twice…….. the Boeing 707.

A. bigger than                                   B. as bigger as         

C. as big as                                        D. more bigger than

8. “Do you know that beautiful lady over there?” “ Yes, that’s Wanida. She’s…………. in her group.”

A. more beautiful than any girl                  B. more beautiful than any other girl

C. so beautiful as other girl             D. beautiful more than another girl

9. My young brother grew very quickly and soon he was……..my mother.

A. more big than                                          B. so big than           

C. as big as                                                    D. too big than

10.He is not…….  tall as his father.

A. the                         B. as                           C. than                       D. more

11. John’s grade……. than his sister’s.

A. higher                    B. more high C. more higher          D. the highest

12. She speaks English as……….as her friend does.

A. good                      B. well                        C. better                     D. the best

13. He works more ………..than I.

            A. slow                       B. slowly                   C. most slowly          D. slowest

14. My book is as……….as yours.

            A. good                      B. well                        C. better                     D. the best

15. I love you……….than I can say.

            A. much                     B. many                     C. more                      D. the most

16. It’s………….to go by bus than by car.

            A. cheaper                 B. cheapest                C. more cheap           D. more cheaper

17. This hotel must be………..than the small one next door.

            A. expensive                                     B. more expensive  

            C. the most expensive                                 D. the more expensive

17. An orange is ……… than a plum.

            A. more large B. more larger           C. larger                     D. the largest

18. This river is……… than that river.

            A. narrow                  B. narrowest              C. narrower   D. most narrow

19. The test is not………difficult……….it was last month.

            A. as/ as                     B. so/ as                     C. more/ as                D. A and B

20. Peter usually drives………..Mary.

            A. more fast              B. more fast than      C. faster than D. B and C

21. The hotel was…….any one we had stayed at before.

            A. more expensive than                              B. more expensive as

            C. most expensive than                               D. better expensive than

22.       A: It’s a long way from Britian, isn’t it?

            B: Yes, but it isn’t as……….as Hong Kong.

            A. far                          B. farther                   C. farthest                  D. further

23. The larger the apartment, the................... the rent.

A. expensive             B. more expensive   C. expensively                      D. most expensive

24. She plays the piano …………… as she sings.

            A. as beautifully                   B. more beautifully

            C. as beautiful                       D. the most beautifully

25. The streets are getting more and …………… these days.

A. crowded                B. less crowded        C. more crowded                 D. most crowded

26. The larger the city, …………… the crime rate.

            A. highest     B. higher      C. the highest              D. the higher

27. You must explain your problems …………....

            A. as clear as you can          B. as clearly as you can     

            C. as clear than you are       D. as clearly as you are     

28. Her grandfather’s illness was…………………..we thought at first.

            A. more seriously as      B. as seriously as            C. more serious than D. as serious than

29. My brother was feeling tired last night, so he went to bed…………..usual.

 

            A. more early than      B. as early as      C more earlier as                D. earlier than

Đỗ Thanh Hải
15 tháng 7 2021 lúc 9:40

IV. Choose the best answer A, B, C, or D to complete each sentence.

1.Ms. Jones isn’t as nice …….. Ms. Smith.

A. as               B. for                          C. like                        D. to

2. The rooms in Graduate Towers are……….. Patterson Hall.

A. larger than                                    B. larger than that of

C. larger than those in                      D. larger than in

3. Although she is very popular, she is not……her sister.

A. pretty as                                        B. as pretty               

C. prettier than                                  D. most pretty than

4. Tuition at an American university runs……. Six thousand dollars a semester.

A. so high as                         B. as high to             

C. as high as                          D. as high than

5. Everyone looks much………. today than they did yesterday.

A. happy                    B. happily                  C. more happily        D. happier

6. Mr. Brown receives a …….. salary than anyone else in the company.

A. big                         B. more bigger          C. bigger                    D. the bigger

7. The Boeing 747 is twice…….. the Boeing 707.

A. bigger than                                   B. as bigger as         

C. as big as                                        D. more bigger than

8. “Do you know that beautiful lady over there?” “ Yes, that’s Wanida. She’s…………. in her group.”

A. more beautiful than any girl                  B. more beautiful than any other girl

C. so beautiful as other girl             D. beautiful more than another girl

9. My young brother grew very quickly and soon he was……..my mother.

A. more big than                                          B. so big than           

C. as big as                                                    D. too big than

10.He is not…….  tall as his father.

A. the                         B. as                           C. than                       D. more

11. John’s grade……. than his sister’s.

A. higher                    B. more high C. more higher          D. the highest

12. She speaks English as……….as her friend does.

A. good                      B. well                        C. better                     D. the best

13. He works more ………..than I.

            A. slow                       B. slowly                   C. most slowly          D. slowest

14. My book is as……….as yours.

            A. good                      B. well                        C. better                     D. the best

15. I love you……….than I can say.

            A. much                     B. many                     C. more                      D. the most

16. It’s………….to go by bus than by car.

            A. cheaper                 B. cheapest                C. more cheap           D. more cheaper

17. This hotel must be………..than the small one next door.

            A. expensive                                     B. more expensive  

            C. the most expensive                                 D. the more expensive

17. An orange is ……… than a plum.

            A. more large B. more larger           C. larger                     D. the largest

18. This river is……… than that river.

            A. narrow                  B. narrowest              C. narrower   D. most narrow

19. The test is not………difficult……….it was last month.

            A. as/ as                     B. so/ as                     C. more/ as                D. A and B

20. Peter usually drives………..Mary.

            A. more fast              B. more fast than      C. faster than D. B and C

21. The hotel was…….any one we had stayed at before.

            A. more expensive than                              B. more expensive as

            C. most expensive than                               D. better expensive than

22.       A: It’s a long way from Britian, isn’t it?

            B: Yes, but it isn’t as……….as Hong Kong.

            A. far                          B. farther                   C. farthest                  D. further

23. The larger the apartment, the................... the rent.

A. expensive             B. more expensive   C. expensively                      D. most expensive

24. She plays the piano …………… as she sings.

            A. as beautifully                   B. more beautifully

            C. as beautiful                       D. the most beautifully

25. The streets are getting more and …………… these days.

A. crowded                B. less crowded        C. more crowded                 D. most crowded

26. The larger the city, …………… the crime rate.

            A. highest     B. higher      C. the highest              D. the higher

27. You must explain your problems …………....

            A. as clear as you can          B. as clearly as you can     

            C. as clear than you are       D. as clearly as you are     

28. Her grandfather’s illness was…………………..we thought at first.

            A. more seriously as      B. as seriously as            C. more serious than D. as serious than

29. My brother was feeling tired last night, so he went to bed…………..usual.

            A. more early than      B. as early as      C more earlier as                D. earlier than

Ánh Mạch
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Nguyễn Lê Phước Thịnh
1 tháng 11 2021 lúc 23:18

Câu 1:
TXĐ:D=R

\(f\left(-x\right)=2\cdot\left(-x\right)^4-3\cdot\left(-x\right)^2+1\)

\(=2x^4-3x^2+1=f\left(x\right)\)

=>f(x) là hàm số chẵn

 

Lê Thị Thu Hồng
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le thai
25 tháng 10 2021 lúc 19:46

1)x>=0

2)v8+5v2-v32+6v1/2=2v2+5v2-4v2+3v2=9v2

3)vx+1=2

x+1=4=>x=3

 

 

Ngoclinhk6
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Đặng Hữu Trang
16 tháng 7 2021 lúc 17:04
ext-9bosssssssssssssssss
Khách vãng lai đã xóa
mai Trương
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Nguyễn Lê Phước Thịnh
26 tháng 10 2023 lúc 21:53

 

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