Question

7​​^1x+2 + 2 . 7^1x-1 = 345

Answer 1

\(7^{^{ }1x+2}+2.7^{1x-1}\)=345

=>7^x.7^2+2.7^x:7=345

=>7^x.(49+2/7)=345

=>7^x.345/7=345

=>7^x=345:345/7

=>7^x=7

=>x=1

vậy x=1

Answer 2

\(7^{1x+2}+2.7^{1x-1}=345\\ \Leftrightarrow7^x.49+2.7^x.\dfrac{1}{7}=345\\ \Leftrightarrow7^x\left(49+\dfrac{2}{7}\right)=345\\ \Leftrightarrow7^x.\dfrac{345}{7}=345\\ \Leftrightarrow7^x=7\\ \Leftrightarrow x=1\)

Vay x=1