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Câu 4:

PTHH: \(NaBr+AgNO_3\rightarrow NaNO_3+AgBr\downarrow\)

a) Ta có: \(n_{AgBr}=\dfrac{37,6}{188}=0,2\left(mol\right)=n_{NaBr}\)

\(\Rightarrow\%m_{NaBr}=\dfrac{0,2\cdot103}{42,6}\cdot100\%\approx48,37\%\) \(\Rightarrow\%m_{NaF}=51,63\%\)

b) Ta có: \(\Sigma n_{AgNO_3}=\dfrac{850\cdot1,09\cdot10\%}{170}=0,545\left(mol\right)\)

\(\Rightarrow n_{AgNO_3\left(dư\right)}=0,345\left(mol\right)\) \(\Rightarrow m_{AgNO_3\left(dư\right)}=0,345\cdot170=58,65\left(g\right)\)

Theo PTHH: \(m_{NaNO_3}=0,2\cdot85=17\left(g\right)\)

Mặt khác: \(\left\{{}\begin{matrix}m_{NaF}=42,6-0,2\cdot103=22\left(g\right)\\m_{dd}=m_{hh}+m_{ddAgNO_3}-m_{AgBr}=931,5\left(g\right)\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}C\%_{AgNO_3\left(dư\right)}=\dfrac{58,65}{931,5}\cdot100\%\approx6,3\%\\C\%_{NaF}=\dfrac{22}{931,5}\cdot100\%\approx2,36\%\\C\%_{NaNO_3}=\dfrac{17}{931,5}\cdot100\%\approx1,83\%\end{matrix}\right.\)

program dung;

uses crt;

var x: integer'

t: real;

begin

clrscr;

write('x= '); readln(x);

t:=(5*x-7)+sqrt(3*x*x+7*x-6);

write('Dien tich la: ',s:1:2);

write('Ket qua: ',t);

readln;

end.

b: \(BC=\sqrt{89}\left(cm\right)\)

\(\sin\widehat{B}=\dfrac{5\sqrt{89}}{89}\)

\(\Leftrightarrow\widehat{B}\simeq32^0\)

\(\widehat{C}=58^0\)

mình làm những bài bn chưa lm nhé

9B

10A

bài 2

have repainted

bàii 3

ride - walikking

swimming

watch

2 have repainted

4 have done 

8 have stepped

9 have you ever played

7) 1 riding -walking

2 swimming

3 watching

8)

2 my mother doesn't like listening to music

5 doing more exercises makes you healthier

còn lại ok nha

chịu ???????????????????

\(a,\dfrac{21\times15\times9}{7\times45\times18}=\dfrac{3\times7\times15\times9}{7\times15\times3\times9\times2}=\dfrac{1}{2}\\ b,\dfrac{24\times11\times27}{33\times8\times12\times9}=\dfrac{12\times2\times11\times3\times9}{11\times3\times8\times2\times6\times9}=\dfrac{12}{8\times6}=\dfrac{12}{48}=\dfrac{1}{4}\)

câu 5: 

x=3,6

y=6,4

câu 6: chụp lại đề

câu 7:

a)ĐKXĐ: \(x\ge0\)

\(3\sqrt{x}=\sqrt{12}\\ \Rightarrow9x=12\\ \Rightarrow x=\dfrac{4}{3}\)

b) ĐKXĐ: \(x\ge6\)

\(\sqrt{x-6}=3\\ \Rightarrow x-6=9\\ \Rightarrow x=15\)

Câu 5: 

Áp dụng định lý Pi-ta-go ta có:

\(AB^2+AC^2=BC^2\\ \Rightarrow BC=\sqrt{6^2+8^2}\\ \Rightarrow BC=10\)

Áp dụng HTL ta có: \(x.BC=AB^2\Rightarrow x.10=6^2\Rightarrow x=3,6\)

Áp dụng HTL ta có: \(x.BC=AC^2\Rightarrow x.10=8^2\Rightarrow x=6,4\)

3. I think collecting stamps is interesting