Tên: Hàn Thiên Tử

Lớp: 9

Link: hoc24.vn/vip/trangle187

1. Tom had a terrible experience last Tuseday

2. He got flat tire on the highway

3. He stood his car for 30 minutes but no one stopped

4. Then he walked 2 miles to a gas station

5. The man there drove him back to his car to fix the tire

6. But haft an hour later, the car broke down again

7. He try to get the engine to start, but nothing happened

I like living in the countryside because of some reasons. Environmentally speaking, it is a peaceful place. The air is fresh. The space is quiet. We can enjoy healthy natural conditions without
worrying much about environmental pollution.

As for social security, the countryside is a safer place than a city. While urban security situation is always complicated with all kinds of crimes, rural areas are much more secure because most of countrymen are friendly and ready to help one another.

Moreover, rural life is also easier that in cities. People in cities are easy to get stressed because of pollution, job pressures, competitions, etc ... On the contrary, those bad things
are very rare in the countryside. To sum up, except income matters, the countryside is a better residence than cities.

\(Fe+H_2SO_4\rightarrow FeSO_4+H_2\\ FeO+H_2SO_4\rightarrow FeSO_4+H_2O\)

nH2=4,48/22,4=0,2(mol)

=>nFe=0,2(mol)=>mFe=0,2.56=11,2(g)

=>mFeO=18,4-11,2=7,2(g)

b)nH2SO4=nH2=0,2(mol)

=>mH2SO4 7%=0,2.98=19,6(g)

=>mH2SO4 =19,6:7%=280(g)

c)mFeSO4=0,2.152=30,4(g)

mdd sau pư=18,4+280-0,2.2=298(g)

=>C%FeSO4=\(\frac{30,4}{298}.100\%\)=10,2%

x=6

Chiều cao miếng đất là :

     288 * 2 : 32 = 18 ( m )

Diện tích sau khi tăng thêm 72 m là :

     288 + 72 = 360 ( m2 )

Cạnh đáy mới sau khi tăng diện tích là :

     360 * 2 : 18 = 40 ( m )

Cạnh đáy phải tăng là :

     40 - 32 = 8 ( m )

             Đáp số : 8m

(3x+1)^2 = (x-1)^2

<=>(3x+1)²-(x-1)²=0

<=>(3x+1-x+1)(3x+1+x-1)=0

<=>(2x+2)4x=0

<=>2(x+1).4x=0

<=>x=0 hoặc x+1=0

<=>x=0 hoặc x=-1

Là khoảng cách hay số đơn vị từ điểm x đến điểm 0 trên trục số

Vì (3;5)=1 nên pt có nghiệm nguyên

\(3x-5y=9\\ \Rightarrow y=\frac{3x-9}{5}=\frac{1-2x}{5}+x-2\)

Đặt t=\(\frac{1-2x}{5}\left(t\in Z\right)\)

\(\Rightarrow x=\frac{1-5t}{2}\)\(=\frac{t-1}{2}+1-3t\)

Đặt n=\(\frac{t-1}{2}\left(n\in Z\right)\)\(\Rightarrow t=2n+1\)

\(\Rightarrow\begin{cases}y=t+x-2\\x=n+1-3t\\t=2n+1\end{cases}\Rightarrow\begin{cases}y=-3n-3\\x=-5n-2\end{cases}\left(n\in Z\right)}}\)