\(3^x+3^{x+2}=3^{2x+2}=810\Rightarrow2x+2=810:3=270\Rightarrow2x=268\Rightarrow x=134\)
\(3^x+3^{x+2}=810\)
\(3^x+3^x.9=810\)
\(3^x\left(1+9\right)=810\)
\(3^x=81\)
\(3^x=3^4\)
\(\Rightarrow x=4\)
\(3^x+3^{x+2}=810\)
\(3^x\times\left(1+3^2\right)=810\)
\(3^x\times\left(1+9\right)=810\)
\(3^x\times10=810\)
\(3^x=\frac{810}{10}\)
\(3^x=81\)
\(3^x=3^4\)
\(x=4\)
Mấy bài này làm zậy ả hả? Ừa cảm ơn nha!!!