Ta có :

\(77^{30}=\left(77^2\right)^{15}=\left(77\cdot77\right)^{15}\)

\(7777^{15}=\left(77\cdot101\right)^{15}\)

Vì \(\left(77\cdot77\right)< \left(77\cdot101\right)\)

\(\Rightarrow\left(77\cdot77\right)^{15}< \left(77\cdot101\right)^{15}\)

\(\Rightarrow77^{30}< 7777^{15}\)