\(3^{x+1}-3^x=54\)
\(3^x\cdot3-3^x=54\)
\(3^x\cdot\left(3-1\right)=54\)
\(3^x\cdot2=54\)
\(3^x=27=3^3\)
\(\Rightarrow x=3\)
Vậy x = 3
\(3^x.\left(3-1\right)=54\)
\(3^x.2=54\)
\(3^x=54:2=27=3^3\)
\(=>x=3\)
\(3^{x+1}-3^x=54\)
\(\Rightarrow3^x\left(3-1\right)=54\)
\(\Rightarrow3^x=27\)
\(\Rightarrow x=3\)