\(\Leftrightarrow3^x\left(3+3^2+3^3\right)=39\cdot3^{30}\)
=>3x=330
hay x=30
`3^[x+1]+3^[x+2]+3^[x+3]=39.3^[30]`
`3^[x].(3+3^2+3^3)=39.3^30`
`3^[x] .39=39.3^[30]`
`3^[x]=3^[30]`
`x=30`
\(3^{x+1}+3^{x+2}+3^{x+3}=39.3^{30}\\ =>3^x.\left(3^1+3^2+3^3\right)=39.3^{30}\\ =>3^x.39=3^{30}.39\\ =>3^x=3^{30}\\ =>x=30\)
`<=> 3^x . 3 + 3^x . 9 + 3^x . 27 = 39 . 3^30`
`=> 3^x(3+9+27) = 39 . 3^30`
`=> 3^x . 39 = 39 . 3^30`
`=> x = 30`