1, chỉ cách làm mẫu nek:

NO+O2=>NO2

NO+O2 là vế 1, NO2 là vế 2

vế 1 : N=1, O=3 

vế 2 : N=1, O=2

cân bằng: 

vế 2: 2O2( O vế 2 ít ng tử hơn ) 

lúc này vế 2 có O=4  vàN=2

vế 1: 2NO 

lúc này vế 1 N=2, O=4

kl : 2NO+O2=>2NO2

2 , làm y như nãy:

4P+5O2=>2P2O5

3, Fe2O3+3H2SO4=>Fe(SO4)3+3H2O

để\(\frac{2x-1}{3+x}\Leftrightarrow\orbr{\begin{cases}\hept{\begin{cases}2x-1< 0\\3+x>0\end{cases}}\\\hept{\begin{cases}2x-1>0\\3+x< 0\end{cases}}\end{cases}}\Leftrightarrow\orbr{\begin{cases}\hept{\begin{cases}x< \frac{1}{2}\\x>-3\end{cases}\left(ktm\right)}\\\hept{\begin{cases}x>\frac{1}{2}\\x< -3\end{cases}\left(tm\right)}\end{cases}}\)

Vậy -3<x<1/2

Để 2x-1/3+x<0 

TH1 : 2x-1<0<=>2x<1<=>x<1/2

    và 3+x>0<=>x> -3 ( ktm)

TH2: 2x-1>0<=> 2x>1<=>x>1/2

    và 3+x<0<=>x< -3  (tm)

vậy -3<x<1/2

mk viết thường nên có chỗ nào ko hiểu thì ib cho mk nha nhớ đó

1, set about: attack someone

2, call back: return to see or collect sth

3, pay me back: return money to someone you borrow

4, go right back to: kiểu nó bắt đầu từ thời Trung Cổ ấy

5, look after: chắc cái này bạn biết nhỉ

6, set about: start doing something

7, turn back: return

8, went about: begin to do something or deal with something

9, called me back: telephone someone again

10, holding back: stating sth

5. 0,024

k nha

Bài 3:

Chiều rộng là:

\(\dfrac{11}{4}-\dfrac{3}{2}=\dfrac{11}{4}-\dfrac{6}{4}=\dfrac{5}{4}\left(m\right)\)

Chu vi là:

\(\left(\dfrac{11}{4}+\dfrac{5}{4}\right)\cdot2=\dfrac{16}{4}\cdot2=4\cdot2=8\left(m\right)\)

Diện tích là:

\(\dfrac{11}{4}\cdot\dfrac{5}{4}=\dfrac{55}{16}\left(m^2\right)\)

bài 1 :

a) \(3\dfrac{4}{5}\)= \(\dfrac{19}{5}\)                                   b) \(4\dfrac{3}{5}\)=\(\dfrac{23}{5}\)

c) \(11\dfrac{12}{13}\)= \(\dfrac{155}{13}\)                              d) 12 \(\dfrac{11}{13}\)= \(\dfrac{167}{13}\)

 

bài 1
a)
\(3\dfrac{4}{5}=\dfrac{3x5+4}{5}=\dfrac{19}{5}\)
b)
\(4\dfrac{3}{5}=\dfrac{4x5+3}{5}=\dfrac{23}{5}\)
c)
\(11\dfrac{12}{13}=\dfrac{11x13+12}{13}=\dfrac{155}{13}\)
d)
\(12\dfrac{11}{13}=\dfrac{12x13+11}{13}=\dfrac{167}{13}\)
bài 2
a)\(3\dfrac{3}{4}+1\dfrac{1}{2}=\dfrac{3x4+3}{4}+\dfrac{1x2+1}{2}=\dfrac{15}{4}+\dfrac{3}{2}=\dfrac{21}{4}\)
b)\(3\dfrac{3}{4}-1\dfrac{1}{2}=\dfrac{15}{4}-\dfrac{3}{2}=\dfrac{15}{4}-\dfrac{6}{4}=\dfrac{9}{4}\)
c)\(3\dfrac{3}{4}x1\dfrac{1}{2}=\dfrac{15}{4}x\dfrac{3}{2}=\dfrac{45}{8}\)
d)\(3\dfrac{3}{4}:1\dfrac{1}{2}=\dfrac{15}{4}:\dfrac{3}{2}=\dfrac{15}{4}.\dfrac{2}{3}=\dfrac{5}{2}\)

Chiều dài hình chữ nhật tàng hình ròi :D

hình chữ nhật trên nào? bn gửi cả hình ảnh nhé!

chưa thấy đề ạ

I find playing online games very interesting. It can support me to feel relaxative after everyday after tired time of learning at school. I usually to play online chess. It is exciting and challenging. It also help me to make friends online. It helps me to think over everything before acting. However, I always limit my time of playing online games. Because I think playing too much online games makes me tired. My eyes are often soring. My mother always reminds me of learning hard, so I know what is the most important to me. Playing online games only helps me to relax a little. So I advise you to working hard at school, and just spend a little time playing online games, although how much you it.

Watching television is one of the activities I like to do in my spare time. I enjoy watching cartoons on Saturday mornings and sports programs on Sunday afternoons. I also watch television during the week after I have finished all my school work. At night, I especially like to watch movies and situation comedies. If I have a lot of homework, I try to arrange my schedule so that I can watch at least one of my favorite shows. Watching television is not the only activity that I do in my spare time. My other favorite activities are making paper flowers and going shopping with my friends. However, when I have spare time, I spend more time watching television than any other activities. Watching television can help me not only relax but also build me a huge knowledge of the open world.”

There are three activities I like to do most in my free time. The first is cartoon. I like watching cartoons very much.I like watching cartoons very much, especially 'Total spies' because it is very exciting and funny. I often watch it with my friends to relax. Second, I also play football with my brother and my friends in our school yard when I have free time. I think football is a sport which helps us have good health and study better.Finally, I like reading books best. Since reading books is helpful, you can learn about another culture and widen your knowledge. Moreover, it is a form of entertainment, which is useful to our life. All in all, I find that if I do not have anything to do in my free time, I will be very bored. Therefore, you should also choose some activities for yourself to do, which help you have a healthy way of life.

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Check it out ~ MDia

- Nếu bạn muốn ngắn thì đây

Going out with friends is my favorite hobby in my free time . I often going out with my friends for eating and chatting. I love chatting with my closed friends, I can share all my stories with them. It’s always filled with laughter and I feel very happy when I am with my friends.

thhi thi đi mà tự làm

Thi tự làm đi chứ bạn

\(v_{tb}=\dfrac{S_1+S_2}{t_1+t_2}=\dfrac{S_1+40\cdot0,5}{0,2+0,5}=\dfrac{S_1+20}{0,7}\)(km/h)

Vì đề không cho S₁ nên mình không thay số đc