hơi mờ

Câu 2 :

\(1.Al_2O_3\\ 2.Fe\left(NO_3\right)_3\\ 3.CuCl_2\\ 4.SO_4\)

Câu 4 : 

a) \(n_{O_2}=\dfrac{1,8.10^{23}}{6.10^{23}}=0,3\left(mol\right)\)

b) \(m_{HCl}=0,5.36,5=18,25\left(g\right)\)

c) \(n_{N_2}=\dfrac{12,395}{22,4}\approx0,6\left(mol\right)\\ m_{N_2}=0,6.28=16,8\left(g\right)\)

d) \(d\dfrac{O_2}{kk}=\dfrac{32}{29}=1,1034>1\)

=> Khí Oxi nặng hơn không khí 1,1034 lần

11 He asked his daughter what kind of sport were you interested in  

12 I asked the neighboor what time your husband left for work 

13) You hate watching violent films , don't you ?

14) They have just repaired the street ìn front of my house,haven't they ?

15) The first TV picture wasn't produced by Baird in 1926,did he ?

16) This kind of shoes was bought last year,didn't she 

My mom asked me how your course took

The man asked me how many students in the class were there 

26.

\(\sqrt{\dfrac{-3}{2a^3}}=\sqrt{\dfrac{-3a}{2a^4}}=\dfrac{1}{a^2}\sqrt{\dfrac{-3a}{2}}\)

Đáp án B

28.

\(\sqrt{\dfrac{a^3}{a}}=\sqrt{a^2}=\left|a\right|=-a\)

Đáp án B

Bài 3: 

a: \(A=\dfrac{3\left(x+4\right)}{\left(x+4\right)\left(x-4\right)}=\dfrac{3}{x-4}\)

b: Để A nguyên thì \(x-4\in\left\{1;-1;3;-3\right\}\)

hay \(x\in\left\{5;3;7;1\right\}\)

Bài 2: 

a: \(=y\left(6x-y\right)\)

b: \(=x\left(y-2\right)+2\left(y-2\right)=\left(y-2\right)\left(x+2\right)\)

c: =(x+2)(x+5)

Câu 1:

Ta có 2x - y = 8 => 2x - y + 9 = 17

Mà 3x + y = 17 => 2x - y + 9 = 3x + y

<=> 9 - y = x + y <=> 9 = x + 2y <=> x = 9 - 2y

Mà 2x - y = 8 => 18 - 4y - y = 8 => 18 - 5y = 8 => y = 2 => x = 5