Đặt \(A=\frac{5^{52}-1}{26}\Rightarrow A=5^{50}-5^{48}+5^{46}-4^{44}+...+5^6-5^4+5^2-1\)
\(A=5^{48}\left(5^2-1\right)+5^{44}\left(5^2-1\right)+...+5^4\left(5^2-1\right)+24\)
\(A=5^{46}.5^2.24+5^{42}.5^2.24+...+5^2.5^2.24+24\)
\(A=100.6.\left(5^{46}+5^{42}+...+5^2\right)+24\)
\(\Rightarrow A\) chia 100 dư 24