\(3^x+3^{x+1}+3^{x+2}=117\)
\(\Rightarrow3^x+3^x\cdot3+3^x\cdot3^2=117\)
\(\Rightarrow3^x+3^x\cdot3+3^x\cdot9=117\)
\(\Rightarrow3^x\cdot\left(1+3+9\right)=117\)
\(\Rightarrow3^x\cdot13=117\)
\(\Rightarrow3^x=\frac{117}{13}\)
\(\Rightarrow3^x=9\)
\(\Rightarrow3^x=3^2\)
\(\Rightarrow x=2\)
2
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mk tk lại
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thank nhiều
yên tâm
\(3^x+3^{x+1}+3^{x+2}=117\)
\(3^x+3^x.3^1+3^x.3^2=117\)
\(3^x.\left(1+3^1+3^2\right)=117\)
\(3^x.13=117\)
\(3^x=117\div13\)
\(3^x=9\)
\(3^x=3^2\)
\(\Rightarrow x=2\)
