Question

3^{x - 1} + 3^x + 3^{x + 1} = 39

Answer 1

\(3^x:3+3^x+3^x\times3=39\)

\(3^x\times\dfrac{1}{3}+3^x+3^x\times3=39\)

\(3^x\times\left(\dfrac{1}{3}+1+3\right)=39\)

\(3^x\times\dfrac{13}{3}=39\)

\(3^x=39:\dfrac{13}{3}\)

\(3^x=9\)

\(3^x=3^2\)

\(x=2\)

 

Answer 2

x=2

Answer 3

3^{x - 1} + 3^x + 3^{x + 1} = 39

3^x.3^-1+3^x+3^x.3=39

3^x.(3^-1+1+3)=39

3^x.\(\dfrac{13}{3}\)=39

3^x=39:\(\dfrac{13}{3}\)

3^x=9

3^x=3²

x=2

Vậy x=2