a)Ta có :\(3^{60}=\left(3^3\right)^{20}=27^{20}\)
\(2^{80}=\left(2^4\right)^{20}=16^{20}\)
Mà \(27^{20}>16^{20}\Leftrightarrow3^{60}>2^{80}\)
b)Ta có :\(5^{20}=\left(5^4\right)^5=625^5\)
\(4^{25}=\left(4^5\right)^5=1024^5\)
Mà \(1024^5>625^5\Leftrightarrow5^{20}< 4^{25}\)