Question

Rút gọn

A=1+5+5²+5³+......+5⁴⁹+5⁵⁰

Answer 1

5A=5+5²+5³+...+5⁵⁰+5⁵¹

5A-A=5⁵¹-1

A=5⁵¹-1:4

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Answer 2

\(\frac{5^{51}-1}{4}\)

Answer 3

A    =1+5+5²+5³+...+5⁴⁹+5⁵⁰

 5A =  5 + 5² + 5³ + 5⁴ + ...+ 5⁵⁰+ 5⁵¹

5A -A =   5 + 5² + 5³ + 5⁴ + ...+ 5⁵⁰+ 5⁵¹  - 1- 5 - 52-53- ... - 549-550

4A= 5⁵¹ -1

A= 5⁵¹ -1 / 4