A = 1 + 5 + 52 + 53 + ... + 550
=> 5A = 5 ( 1 + 5 + 52 + 53 + ... + 550 )
= 5 + 52 + 53 + 54 + ... + 551
=> 5A - A = ( 5 + 52 + 53 + 54 + ... + 551 ) - ( 1 + 5 + 52 + 53 + ... + 550 )
4A = 551 - 1
\(\Rightarrow A=\frac{5^{51}-1}{4}\)
5A = 5 + 52 + 53 + 54 + 55 +...+ 551
A = 1 + 5 + 52 + 53 + 54 +...+ 550
5A - A =(5 + 52 + 53 + 54 + 55 +...+ 551) - (1 + 5 + 52 + 53 + 54 +...+ 550)
4A = 551 - 1
A = (551 - 1) : 4