Question

Tìm x biết  \(2.7^{x-1}+7^{x+2}=345\)

Answer 1

2.7^x-1+7^x+2=345

=> 7^x-1.(2+7³)=345

=> 7^x-1.345=345

=> 7^x-1=1

=> 7^x-1=7⁰

=> x-1=0

=> x=1

Answer 2

\(\Rightarrow7^{x-1}.\left(2+7^3\right)=345\)

\(\Rightarrow7^{x-1}.345=345\)

\(\Rightarrow7^{x-1}=1\)

\(\Rightarrow7^{x-1}=7^0\)

=> x-1=0

=> x=1