):< no

thanks

Ủa sao bạn mất nick ???

mơ đê :>>

ok 

ok

ảnh mô

OK

:'')

um...

\(\dfrac{\dfrac{3}{5}.7^2-3.5^6+\dfrac{3}{5}.3^9}{\dfrac{3}{4}.7^2-\dfrac{3}{4}.5^7+\dfrac{3}{4}.3^9}=\dfrac{\dfrac{3}{5}.7^2-\dfrac{3}{5}.5^7+\dfrac{3}{5}.3^9}{\dfrac{3}{4}.7^2-\dfrac{3}{4}.5^7+\dfrac{3}{4}.3^9}\)

\(=\dfrac{\dfrac{3}{5}\left(7^2-5^7+3^9\right)}{\dfrac{3}{4}\left(7^2-5^7+3^9\right)}=\dfrac{3}{5}:\dfrac{3}{4}=\dfrac{3}{5}.\dfrac{4}{3}=\dfrac{4}{5}\)

\(=\dfrac{3\left(\dfrac{1}{5}\cdot49-5^6+\dfrac{1}{5}\cdot3^9\right)}{3\left(\dfrac{1}{4}\cdot7^2-\dfrac{1}{4}\cdot5^7+\dfrac{1}{4}\cdot3^9\right)}=\dfrac{3\cdot\dfrac{-58393}{5}}{3\cdot\dfrac{-58393}{4}}\)

\(=\dfrac{4}{5}\)

\(a,\Leftrightarrow3^{x-2}\left(18+3^2\right)=243\\ \Leftrightarrow3^{x-2}=243:27=9=3^2\\ \Leftrightarrow x-2=2\Leftrightarrow x=4\)

\(18\cdot3^{x-2}+3^x=243\)

\(\Leftrightarrow3^{x+1}=243\)

hay x=4

\(18.3^{x-2}+3^x=243\)

=> \(3^2.2.3^x:3^2+3^x=243\)

\(\Rightarrow2.3^x+3^x=243\)

=> \(3^{x+1}=243=3^5\)

=> x + 1 = 5

=> x = 4

Câu 8: 

=>2,5y=260

hay y=104

Câu 10:

Tỉ số phần trăm giữa số bạn nữ và số bạn nam là:

25:10=250%