1.

a, \(Natri+sulfuric\:acid\rightarrow Natri\text{ }sulfat+Hidro\)

b, PTHH: \(2Na+H_2SO_4\rightarrow Na_2SO_4+H_2\uparrow\)

Câu 1:

\(a,\) sodium + sulfuric acid ---> sodium sulfate + hydrogen

\(b,2Na+H_2SO_4\to Na_2SO_4+H_2\)

Câu 2:

\(a,\) iron sulfate + barium chloride -----> barium sulfate + iron chloride

\(b,Fe_2\left(SO_4\right)_3+3BaCl_2\to3BaSO_4\downarrow+2FeCl_3\)

Câu 1: 

a,MCD: R1//R2

\(R_{12}=\dfrac{R_1R_2}{R_1+R_2}=\dfrac{30\cdot20}{30+20}=12\left(\Omega\right)\)

b, MCD: R3nt(R1//R2)

\(R_{tđ}=R_3+R_{12}=30+12=42\left(\Omega\right)\)

Câu 2

a Điện trở và cường độ dòng điện tối đa mà biến trở đó có thể có

b,\(S=\dfrac{l\cdot\rho}{R}=\dfrac{100\cdot1,1\cdot10^{-6}}{200}=5,5\cdot10^{-7}\)

\(R=\sqrt{\dfrac{S}{\pi}}=\sqrt{\dfrac{5,5\cdot10^{-7}}{\pi}}=4,18\cdot10^{-4}\left(m\right)=0,418\left(mm\right)\)

Bài 1:

\(a,Magnesium+Oxygen\xrightarrow{t^o}Magnesium Oxide\\ b,m_{Mg}+m_{O_2}=m_{MgO}\\ c,m_{O_2}=m_{MgO}-m_{Mg}=15-9=6(g)\)

Bài 2:

\(a,Sulfur+Oxygen\xrightarrow{t^o}\text {Sulfur dioxide}\\ b,m_{S}+m_{O_2}=m_{SO_2}\\ c,m_{O_2}=m_{SO_2}-m_{S}=6,4-3,2=3,2(g)\)

Bài 3:

\(a,zinc+\text{hydrochloric acid}\to \text {zinc chloride}+hydrogen\\ b,m_{Zn}+m_{HCl}=m_{ZnCl_2}+m_{H_2}\\ c,m_{HCl}=m_{ZnCl_2}+m_{H_2}-m_{Zn}=13,6+0,2-6,5=7,3(g)\)

Ai giúp tui với 

Bài 5: 

b) Xét tứ giác AHCK có 

\(\widehat{AHC}\) và \(\widehat{AKC}\) là hai góc đối

\(\widehat{AHC}+\widehat{AKC}=180^0\left(90^0+90^0=180^0\right)\)

Do đó: AHCK là tứ giác nội tiếp(Dấu hiệu nhận biết tứ giác nội tiếp)

hay \(\widehat{AKH}=\widehat{ACH}\)(Cùng nhìn cạnh AH)

1 makes

2 doesn't eat

3 goes

4 Do-go

5 Do-agree

6 does-come

7 does-work

8 doesn't -water

9 do-do

10 Do they eat

11 am 

12 rises

13 is

14 doesn't read

15 watches

Ex2

1. you don't go to school everyweekday

Do you go to school every weekday?

2. Lan doesn't play badminton with her friends today

Does Lan  play badminton with her friends today?

3. Hoa doesn't like reading story books

Does Hoa like reading story books

4. Lien and Lan don't in the same class

Do Lien and Lan in the same class

5.  Ba's father doesn't work in a big factory with my father

Does  Ba's father work in a big factory with my father

6 She doesn't study English very well

Does she study English very well

7 They don't tall and thin

Do they tall and thin

8 His mother doesn't cook dinner for the family everyday

Does his mother cook dinner for the family everyday

9 Hoa's mother doesn't go shopping this morning

Ex3

1. Lan usually reads book recess

2 Does Ba go to the market every Sunday

3 Her father often rides his motorbike

4 Nam doesn't have short black hair

5 She usually gets up early

\(ĐK:x\in R\\ PT\Leftrightarrow\sqrt{\left(x+\dfrac{1}{2}\right)^2}=7-2x\\ \Leftrightarrow\left|x+\dfrac{1}{2}\right|=7-2x\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=7-2x,\forall x+\dfrac{1}{2}\ge0\\x+\dfrac{1}{2}=2x-7,\forall x+\dfrac{1}{2}< 0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{13}{6},\forall x\ge-\dfrac{1}{2}\left(tm\right)\\x=\dfrac{15}{2},\forall x< -\dfrac{1}{2}\left(ktm\right)\end{matrix}\right.\Leftrightarrow x=\dfrac{13}{6}\)