Câu 2

\((1) MnO_2 + 4HCl \to MnCl_2 + Cl_2 + 2H_2O\\ (2) Cl_2 + H_2 \xrightarrow{as} 2HCl\\ (3) 3Cl_2 + 2Fe \xrightarrow{t^o} 2FeCl_3\\ (4) 2FeCl_3 + Fe \to 3FeCl_2\\ (5) 2NaOH + Cl_2 \to NaCl + NaClO + H_2O\)

\((1) 4Al + 3O_2 \xrightarrow{t^o} 2Al_2O_3\\ (2) 2Fe + 3Cl_2 \xrightarrow{t^o} 2FeCl_3\\ (3) C + O_2 \xrightarrow{t^o} CO_2\\ (4) 2KMnO_4 \xrightarrow{t^o} K_2MnO_4 + MnO_2 + O_2\\ (5) 4P + 5O_2 \xrightarrow{t^o} 2P_2O_5\\ (6) 2KClO_3 \xrightarrow{t^o} 2KCl + 3O_2\\ (7) Fe + H_2SO_4 \to FeSO_4 + H_2\\ (8) Cu + 2H_2SO_4 \to CuSO_4 + SO_2 + 2H_2O\\ (9) 2Fe + 6H_2SO_4 \to Fe_2(SO_4)_3 + 3SO_2 + 6H_2O\\ (10) 2Al + 6H_2SO_4 \to Al_2(SO_4)_3 + 3SO_2 + 6H_2O\)

Có ABCD không

Câu 23 là C

Bạn ơi, kiểm tra phải tự làm chứ

\(=8\cdot25-72:9=200-8=192\)

= 8 . 25 - 72 : 9

= 200 - 8

= 192

\(x+\sqrt{4-x^2}=2\)

\(\Leftrightarrow4-x^2=\left(2-x\right)^2\)

\(\Leftrightarrow4-x^2=4-8x+x^2\)

\(\Leftrightarrow4-x^2-4+8x-x^2=0\)

\(\Leftrightarrow8x-2x^2=0\)

\(\Leftrightarrow2x\left(4-x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\4-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

\(x+\sqrt{1-x^2}=1\)

\(\Leftrightarrow1-x^2=\left(1-x\right)^2\)

\(\Leftrightarrow1-x^2=1-2x+x^2\)

\(\Leftrightarrow1-x^2-1+2x-x^2=0\)

\(\Leftrightarrow2x-2x^2=0\)

\(\Leftrightarrow2x\left(1-x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\1-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)

Câu 1:

a: ĐKXĐ: x+3<>0

=>x<>-3

b: ĐKXĐ: \(\begin{cases}2-x\ge0\\ x+5\ge0\end{cases}\Rightarrow\begin{cases}x\le2\\ x\ge-5\end{cases}\)

=>-5<=x<=2

c: ĐKXĐ: 2-x>0 và x+2>=0

=>x<2 và x>=-2

=>-2<=x<2

Câu 3:

a: \(\frac{3x+1}{2}-\frac{x-2}{3}<\frac{1-2x}{4}\)

=>\(\frac{6\left(3x+1\right)}{12}-\frac{4\left(x-2\right)}{12}<\frac{3\left(1-2x\right)}{12}\)

=>6(3x+1)-4(x-2)<3(1-2x)

=>18x+6-4x+8<3-6x

=>14x+14<3-6x

=>20x<-11

=>x<-11/20

b: \(\left(x+1\right)\left(2x+2\right)-2\ge x^2+\left(x-1\right)\left(x+2\right)\)

=>\(2x^2+4x+2-2\ge x^2+x^2+x-2\)

=>4x>=x-2

=>3x>=-2

=>x>=-2/3

e: \(\begin{cases}x+3>7-2x\\ 4+4x>6x-1\end{cases}\Rightarrow\begin{cases}x+2x>7-3\\ 4x-6x>-1-4\end{cases}\)

=>\(\begin{cases}3x>4\\ -2x>-5\end{cases}\Rightarrow\begin{cases}x>\frac43\\ x<\frac52\end{cases}\)

=>4/3<x<5/2

cái này áp dụng hệ thức lượng thôi bạn

AH=căn 6^2-4,8^2=3,6cm

=>AC=6^2/3,6=10cm

dạ em cám onnnn