+ Xét hh X : \(M_X=16\cdot3=48\)(g/mol)

Dùng phương pháp đường chéo:

SO2:64 O2:32 48 16 16 = 1 1

=> \(hhX\hept{\begin{cases}10\left(l\right)SO_2\\10\left(l\right)O_2\end{cases}}\)

=> \(hhY\hept{\begin{cases}8\left(l\right)SO_2\\10\left(l\right)O_2\end{cases}}\)=> \(M_Y=\frac{64\cdot8+32\cdot10}{18}=\frac{416}{9}\) (g/mol)

=> \(\frac{d_X}{d_Y}=\frac{M_X}{M_Y}=\frac{48}{\frac{416}{9}}=\frac{27}{26}\)

thank you, mình được thầy chữa r bn ms giải, tốt quá :((((

\(\frac{x^2-49}{x-7}+x-2=\frac{\left(x-7\right)\left(x+7\right)}{x-7}+\frac{\left(x-2\right)\left(x-7\right)}{x-7}\)

\(=\frac{\left(x-7\right)\left[\left(x+7\right)+\left(x-2\right)\right]}{x-7}=\frac{\left(x-7\right)\left(2x+5\right)}{x-7}=2x+5\)

Đặt \(2x+5=0\Leftrightarrow x=-\frac{5}{2}\)

Vậy \(x=-\frac{5}{2}\)

co2 + h2o <----> h2co3

bằng H2C03

a, \(4x^2-4xy+y^2=\left(2x-y\right)^2\)

b, \(a^3-9a^2+27a-27=\left(a-3\right)^3\)

c, \(\left(2m-3n\right)^2-\left(2m+3n\right)^2=\left(2m-3n-2m-3n\right)\left(2m-3n+2m+3n\right)\)

\(=-6n.4m=-24mn\)

d, \(x^2+x-6=x^2+3x-2x-6=\left(x-2\right)\left(x+3\right)\)

1. He love watching film(Lik e)

=> He lik e watching film

2. He has finished exercise since yesterday(past simple)

=> He finished exercise yesterday

3. He presented this topic more successfully than his friend(less)

=> His friend presented this topic less successfully than him

4. It rains heavily we won't held the english club (IF)

=> If rains don't heavily , we will  held the english club

5. they built the building 10 years ago(present perfect)

=>  They have built  the building for 10 years