Question

Tính tổng S S=1+5+5 mũ 2+5 mũ +...+5 mũ 2019

Answer 1

S=1+5+5^2+5^3+...+5^2019

=>5S=5+5^2+5^3+5^4+...+5^2020

  -

  S=1+5+5^2+5^3+...+5^2019

4S=5^2020-1

=>S=5^2020:4-1/4

Answer 2

S = 1 + 5 + 5^2 + 5^3 + ...+ 5^2019

=> 5S = 5 + 5^2 + 5^3 + 5^4 + ...+ 5^2020

=> 5S-S = 5^2020 - 1

4S = 5^2020 - 1

\(S=\frac{5^{2020}-1}{4}\)