Question

Tìm x. 3^x+1+3^x+3=810

Answer 1

\(3^{x+1}+3^{x+3}=810\Leftrightarrow3^{x+1}+3^2.3^{x+1}=810\Leftrightarrow10.3^{x+1}=81.10\)

\(\Leftrightarrow3^{x+1}=81=3^4\Leftrightarrow x+1=4\Leftrightarrow x=3\)