a/ \(5^x+5^{x+2}=650\)
\(\Leftrightarrow5^x\left(1+5^2\right)=650\)
\(\Leftrightarrow5^x=25\)
\(\Leftrightarrow5^x=5^2\)
\(\Leftrightarrow x=2\)
Vậy..
b/ \(2^{91}=\left(2^{13}\right)^7=8192^7\left(1\right)\)
\(5^{35}=\left(5^5\right)^7=3125^7\left(2\right)\)
Từ \(\left(1\right)+\left(2\right)\Leftrightarrow2^{91}>5^{35}\)