Bài 3 : 

(A) : Fe3O4

(B) : FeO

(D)  : Fe

(E) : FeS

(F)  : SO2

(G) : SO3

(H) : H2SO4

\(3Fe_2O_3 + CO \xrightarrow{t^o} 2Fe_3O_4 + CO_2\\ Fe_3O_4 + CO \xrightarrow{t^o} 3FeO + CO_2\\ FeO + CO \xrightarrow{t^o} Fe +C O_2\\ Fe + S \xrightarrow{t^o} FeS\\ 4FeS +75O_2 \xrightarrow{t^o} 2Fe_2O_3 +4SO_2\\ 2SO_2 + O_2 \xrightarrow{t^o} 2SO_3\\ SO_3 + H_2O \to H_2SO_4\\ 2FeS + 10H_2SO_4 \to Fe_2(SO_4)_3 + 9SO_2 + 10H_2O\)

Cảm ơn bạn rất nhiều!!! 

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

\(\left\{{}\begin{matrix}2x+2y=18\\x-y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x+y=9\\x-y=-6\end{matrix}\right.\Leftrightarrow}\left\{{}\begin{matrix}2x=3\\x-y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{3}{2}\\y=\dfrac{15}{2}\end{matrix}\right.\)\(\left\{{}\begin{matrix}2x+3y=6\\x-2y=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}4x+6y=12\\3x-6y=9\end{matrix}\right.\Leftrightarrow}\left\{{}\begin{matrix}7x=21\\3x-6y=9\end{matrix}\right.\Leftrightarrow}\left\{{}\begin{matrix}x=3\\y=0\end{matrix}\right.\)

Lỗi latex kìa .-.

a: Ta có: \(\hat{OAM}+\hat{MAN}+\hat{NAO^{\prime}}=180^0\)

=>\(\hat{OAM}+\hat{O^{\prime}AN}=180^0-90^0=90^0\)

=>\(\hat{OMA}+\hat{O^{\prime}NA}=90^0\)

ΔAMN vuông tại A

=>\(\hat{AMN}+\hat{ANM}=90^0\)

\(\hat{O^{\prime}NM}+\hat{OMN}\)

\(=\hat{O^{\prime}NA}+\hat{OMA}+\hat{AMN}+\hat{ANM}=90^0+90^0=180^0\)

mà hai góc này là hai góc ở vị trí trong cùng phía

nên OM//O'N

a A>B

b C>D 

c D<E

12. D
13. C

14. D

D

C

D

hơi mờ