b: Tọa độ giao là:

5x-4=2x+2 và y=2x+2

=>x=2 và y=6

c: Vì (d2)//d nên (d2): y=2x+b

Thay x=1 và y=3 vào (d2), ta được:

b+2=3

=>b=1

Ta có:
\(\dfrac{x}{10}=\dfrac{y}{5}\)
\(\Rightarrow\dfrac{x}{20}=\dfrac{y}{10}\)  \(\left(1\right)\)
\(\dfrac{y}{2}=\dfrac{z}{3}\)
\(\Rightarrow\dfrac{y}{10}=\dfrac{z}{15}\)  \(\left(2\right)\)
Từ \(\left(1\right)\) và \(\left(2\right)\)
\(\Rightarrow\dfrac{x}{20}=\dfrac{y}{10}=\dfrac{z}{15}\)
Lại có:
\(\dfrac{z}{15}=\dfrac{4z}{60}\)
Áp dụng tính chất của dãy tỉ số bằng nhau,ta có:
\(\dfrac{x}{20}=\dfrac{y}{10}=\dfrac{4z}{60}=\dfrac{x+4z}{20+60}=\dfrac{240}{80}=3\)
\(\Rightarrow x=3\cdot20=60\)
     \(y=3\cdot10=30\)
     \(z=3\cdot15=45\)

Bài 1:

Theo đề ta có : A₁=G₁; T₁=3A₁; X₁ = 2T₁

=>\(\left\{{}\begin{matrix}X_1=6A_1\\T_1=3A_1\\G_1=A_1\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}A=4A_1\\G=7A_1\end{matrix}\right.\)

Lại có: 2A + 3G= 5800

=> 29A₁ = 5800 => A₁=200

=> G = 1400

a) 

4Na + O₂ ---t^o→ 2Na₂O

Na₂O + H₂O → 2NaOH

2NaOH + CO₂ → Na₂CO₃ + H₂O

Na₂CO₃ + Ca(OH)₂ → 2NaOH + CaCO₃

CaCO₃ ---t^o→ CaO + CO₂

CO₂ + NaOH → NaHCO₃ 

NaHCO₃ + H₂SO₄ → Na₂SO₄ + CO₂ + H₂O

Na₂SO₄ + Ba(OH)₂ → 2NaOH + BaSO₄

b) 

S + O₂ ---t^o→ SO₂

2SO₂ + O₂ ---t^o(V₂O₅)→ 2SO₃

SO₃ + H₂O → H₂SO₄

H₂SO₄ + Cu(OH)₂ → CuSO₄ + 2H₂O

CuSO₄ + FeCl₂ → CuCl₂ + FeSO₄

FeSO₄ + 2NaOH → Fe(OH)₂ + Na₂SO₄

Fe(OH)₂ + 2HCl → FeCl₂ + 2H₂O

2FeCl₂ + Cl₂ → 2FeCl₃

2FeCl₃ + 3Ba(OH)₂ → 2Fe(OH)₃ + 3BaCl₂

2Fe(OH)₃ ---t^o→ Fe₂O₃ + 3H₂O

 Fe₂O₃ + 3H₂SO₄ → Fe₂(SO₄)₃ + 3H₂O

câu d tìm ra x,y là bao nhiêu

a: \(\left\{{}\begin{matrix}3x+6y=4\\x+4y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3x+6y=4\\3x+12y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{1}{3}\\x=2-\dfrac{4}{3}=\dfrac{2}{3}\end{matrix}\right.\)

7. How often does he go to the library?
8. ....is the shortest student in his class.
9......is her address?
10... is shorter than Ba.

7 how often does he go to the library

8 nga is the shortest student in the class

9 what is her adress

10 hoa is shorter than ba

em cắt bớt đi

2 She said nothing grew in her garden because it never got any sun

3 He told his mother he was going to HN the day after

6 He told her to switch off the TV

9 I warned them not to watch late night horror film