Question

Giúp mình con tính này với: 

3^x-1 + 3^x + 3^x+1 = 39 Bài tìm x nha

Answer 1

\(\Leftrightarrow3^{x-1}\left(1+3+3^2\right)=39\\ \Leftrightarrow3^{x-1}\cdot13=39\\ \Leftrightarrow3^{x-1}=3=3^1\\ \Leftrightarrow x-1=1\Leftrightarrow x=2\)

Answer 2

\(\Leftrightarrow3^x\cdot\dfrac{13}{3}=39\)

\(\Leftrightarrow x=2\)

Answer 3

\(3^{x-1}+3^x+3^{x+1}=39\\ \Rightarrow3^x:3+3^x+3^x.3=39\\ \Rightarrow3^x.\dfrac{1}{3}+3^x+3^x.3=39\\ \Rightarrow3^x\left(\dfrac{1}{3}+1+3\right)=39\\ \Rightarrow3^x.\dfrac{13}{3}=39\\ \Rightarrow3^x=9\\ \Rightarrow3^x=3^2\\ \Rightarrow x=2\)

Answer 4

x bằng 2

Answer 5

x  =  2

ok