Question

tìm x biết 

3^x + 3^x+1 +3^x +2 117

Answer 1

     \(3^x+3^{x+1}+3^{x+2}=117\)

\(\Leftrightarrow3^x+3^x.3^1+3^x.3^2=117\)

\(\Leftrightarrow3^x\left(1+3+3^2\right)=117\)

\(\Leftrightarrow3^x.13=117\)

\(\Leftrightarrow3^x=9=3^2\)

\(\Leftrightarrow x=2\)

Answer 2

3^x+3^x+1+3 ^x+2=117

=> 3^x .(1+3+3^2 )=117

=> 3^x .(1+3+9)=117

=> 3^x .13=117

=> 3^x=117:13

=> 3^x=9

=> 3^x=3^2

Vậy x=2