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\(2.3^x+5.3^x.3=153\Leftrightarrow2.3^x+15.3^x=153\)
\(\Leftrightarrow17.3^x=153\Leftrightarrow3^x=9\Leftrightarrow x=2\)
\(\Leftrightarrow2.3^x+5.3.3^x=153\)
\(\Leftrightarrow17.3^x=3^2.17\)
\(\Leftrightarrow3^x=3^2\Rightarrow x=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
2/5.3x-1/2-1/4=1/5
=>2/5.3x-1/4=1/5
=>2/5.3x=1/5+1/4
=>2/5.3x=9/20
=>3.x=9/20:2/5
=>3.x=9/8
=>x=9/8:3
=>x=3/8
vay x=3/8
2/5.3x-1/2-1/4 = 1/5
=> 2/5.3x = 1/5+1/4+1/2
2/5.3x = 19/20
3x = (19/20):(2/5)
3x = 19/8
x = (19/8):3
x = 19/24
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời:
\(3x+1+5\times3x+2=144\)
\(\Leftrightarrow3x+1+15x+2=144\)
\(\Leftrightarrow18x=141\)
\(\Leftrightarrow x=\frac{47}{8}\)
Vậy \(x=\frac{47}{8}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Leftrightarrow3.3^x-\dfrac{3^x}{3}=72\)
\(\Leftrightarrow9.3^x-3^x=3.72\)
\(\Leftrightarrow8.3^x=3.8.3^2\)
\(\Leftrightarrow3^x=3^3\Rightarrow x=3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(3^{x+2}-3^x=72\)
\(\Rightarrow3^x\cdot\left(3^2-1\right)=72\)
\(\Rightarrow3^x\cdot\left(9-1\right)=72\)
\(\Rightarrow3^x\cdot8=72\)
\(\Rightarrow3^x=\dfrac{72}{8}\)
\(\Rightarrow3^x=9\)
\(\Rightarrow3^x=3^2\)
\(\Rightarrow x=2\)
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Xem lại đề
![](https://rs.olm.vn/images/avt/0.png?1311)
(3x - 3009) + 72 = 72
3x - 3009 = 72 - 72
3x - 3009 = 0
3x = 3009
x = 1003
\(3^x+5.3^{x-1}=72\)
=> \(3^{x-1}.3+5.3^{x-1}=72\)
=> \(3^{x-1}.\left(3+5\right)=72\)
=> \(3^{x-1}.8=72\)
=> \(3^{x-1}=72:8\)
=> \(3^{x-1}=9\)
=> \(3^{x-1}=3^2\)
=> \(x-1=2\)
=> \(x=2+1\)
=> \(x=3\)
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