3x+1+3x+2=324
3x.3+3x.32=324
3x.(3+32)=324
3x.12=324
3x=324:12
3x=27
3x=33
x=3
\(3^{x+1}+3^{x+2}=324\)
\(3^x.3+3^x.3^2=324\)
\(3^x\left(3+3^2\right)=324\)
\(3^x\left(3+9\right)=324\)
\(3^x
.
12=324\)
\(3^x\) \(=324
:
12\)
\(3^x\) \(=27\)
\(3^x\) \(=3^3\)
\(\Rightarrow x=3\)