\(99^{20}=\left(99^2\right)^{10}=\left(99\times99\right)^{10}< \left(99\times101\right)^{10}=9999^{10}\)
Vậy 9920 < 999910
Chúc bạn học tốt ^^
Ta có: \(^{99^{20}}\)=\(99^{2.10}\)=\(9081^{10}\)
Vì \(9081^{10}\) <\(9999^{10}\)
nên \(99^{20}\)<\(9999^{10}\)
ta có: \(9999=99\cdot101\)
Do đó: \(9999^{10}=99^{10}\cdot101^{10}\)
=> \(99^{20}=99^{10}\cdot99^{10}\)
Vì \(99^{10}\cdot99^{10}< 99^{10}\cdot101^{10}\)nên \(99^{20}< 101^{10}\)
Vậy: \(99^{20}< 9999^{10}\)