1. Where is the book?

2. What did they look after a long walk?

3. What make people different from all other animals?

4. Who is Jane waiting for?

5. Why did you have to cancel your picnic?

6. How long does it take to ride to VT by motorbike?

7. Who is Mimi talking to Fred about?

8. How often do you go to E club?

9. Why do you often go for a walk at night?

10. Where are you going for holiday this summer?

11. Who is your father going to take to the zoo next Sunday?

12. What do you study English for?

Câu 12:

C₅H₁₂ → C₅H₁₁Cl

CTCT: \(CH_3CH_2CH_2CH_2CH_2Cl\)

\(CH_3CHClCH_2CH_2CH_3\)

\(CH_3CH_2CHClCH_2CH_3\)

→ Đáp án: C.

Câu 13:

Gọi CTPT của X là C_nH_2n.

Ta có: \(n_{C_2H_6}.30+n_X.14n=14,6\left(1\right)\)

m _{bình tăng} = m_X = 5,6 (g) = n_X.14n (2)

Từ (1) và (2) \(\Rightarrow n_{C_2H_6}.30+5,6=14,6\Rightarrow n_{C_2H_6}=0,3\left(mol\right)\)

Mà: Thể tích hh A giảm đi 1/4 

\(\Rightarrow\dfrac{V_X}{V_X+V_{C_2H_6}}=\dfrac{1}{4}\Rightarrow\dfrac{n_X}{n_X+n_{C_2H_6}}=\dfrac{1}{4}\Rightarrow n_X=0,1\left(mol\right)\)

Thay vào (2), được n = 4.

Vậy: X là C₄H₈.

→ Đáp án: D

(12-12)-(57-57) nha

(12-12)-(57-57) nhé, khi đổi chỗ các số thì bạn nên nhớ vẫn giữ nguyên dấu, còn chuyển vế mới đổi dấu nha

Trả lời:

(cái nào cũng được bạn ơi)

[ 12 + ( - 57 ) ] - [ - 57 - ( - 12 ) ]

= ( 12 - 57 ) - ( - 57 + 12 )

= 12 - 57 + 57 - 12

= (12 - 12 ) - ( 57 - 57 )

= 0 - 0 

= 0

11) \(\dfrac{2\sqrt{3}-\sqrt{15}}{\sqrt{3}}\)

\(=\dfrac{\left(2\sqrt{3}-\sqrt{15}\right)\sqrt{3}}{\sqrt{3}\cdot\sqrt{3}}\)

\(=\dfrac{2\cdot\sqrt{3}\cdot\sqrt{3}-\sqrt{15}\cdot\sqrt{3}}{3}\)

\(=\dfrac{6-3\sqrt{5}}{3}\)

\(=2-\sqrt{5}\)

12) \(\dfrac{2\sqrt{2}+\sqrt{2}}{5\sqrt{2}}\)

\(=\dfrac{3\sqrt{2}}{5\sqrt{2}}\)

\(=\dfrac{3}{5}\)

11: \(=\dfrac{\sqrt{3}\left(2-\sqrt{5}\right)}{\sqrt{3}}=2-\sqrt{5}\)

12: \(=\dfrac{3\sqrt{2}}{5\sqrt{2}}=\dfrac{3}{5}\)

Ta có:

\(v_{tb}=\dfrac{S_1+S_2}{t_1+t_2}=\dfrac{S}{\dfrac{S_1}{v_1}+\dfrac{S_2}{v_2}}=\dfrac{S}{\dfrac{\dfrac{1}{2}S}{v_1}+\dfrac{\dfrac{1}{2}S}{v_2}}=\dfrac{S}{\dfrac{S}{2\cdot12}+\dfrac{S}{2\cdot20}}=15\)km/h

Chọn A

D

8d

9c

10d

11a

12d

a: =-10/13-3/13+5/17+12/17-11/20=-11/20

b: =9/4-10/12+11/12=10/12=5/6

c: =(-7+8)/15=1/15

d: =-9/15+10/15=1/15

e: \(=\dfrac{-10}{36}+\dfrac{20}{35}-\dfrac{11}{36}=\dfrac{-42}{36}=-\dfrac{7}{6}\)

f: \(=\dfrac{-7}{21}+\dfrac{8}{24}=\dfrac{1}{3}-\dfrac{1}{3}=0\)

dg thi?