Em đăng câu hỏi `1.9` sang câu khác nhé^^

`a, x/3 =7/9`

`=> 9x=3.7`

`=> 9x=21`

`=>x= 21/9`

`=> x= 7/3`

__

`b, 8/x = 5/35`

`=> 8/x = 1/7`

`=> x=8.7`

`=> x= 56`

__

`c,(2x-5)/39 = 6/27`

`=> (2x-5).27=6.39`

`=> (2x-5).27=234`

`=> 2x-5= 234:27`

`=>2x-5=26/3`

`=> 2x= 26/3 +5`

`=>2x=41/3`

`=>x=41/3 : 2`

`=>x=41/6`

__

`d,(x+3)/13 = 7/39`

`=> (x+3).39 = 7.13`

`=> (x+3).39=91`

`=> x+3=91:39`

`=>x+3=7/3`

`=>x=7/3-3`

`=>x=-2/3`

khong vô đc kiểu=')

\(2^x+2^{x+1}=48\\ \Rightarrow2^x+2^x\cdot2^1=48\\ \Rightarrow2^x\left(1+2\right)=48\\ \Rightarrow2^x\cdot3=48\\ \Rightarrow2^x=48:3\\ \Rightarrow2^x=16\\ \Rightarrow2^x=2^4\\ \Rightarrow x=4\)

Vậy `x=4`

\(\left(x-2\right)\cdot\left(x-3\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-2=0\\x-3=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=2\\x=3\end{matrix}\right.\)

Vậy \(x\in\left\{2;3\right\}\)

\(3^{x+1}-3^x=1428\\ \Rightarrow3^x\cdot3^1-3^x=1428\\ \Rightarrow3^x\left(3-1\right)=1428\\ \Rightarrow3^x\cdot2=1428\\ \Rightarrow3^x=1428:2\\ \Rightarrow3^x=714\)

Em xem lại đề nhé^^