Bạn tham khảo : $C = 1+5+5^2+5^3+…+5^{2020}$ $5C = 5+5^2+5^3+5^4+ … +5^{2021}$ $5C -C = (5+5^2+5^3+5^4+ … +5^{2021}) -(1+5+5^2+5^3+…+5^{2020})$ $4C = 5^{2021} – 1$ $C = \dfrac{5^{2021} – 1}{4}$ Bình luận
$c=1+5+5^2 + 5 ^3 + …. + 5 ^ {2020}$ $5c = 5 + 5^2 + 5^3 + 5^4 +……..+ 5^ {2021}$ Ta lấy : $5c – c$ 4c = $5^{2021}-1$ $c =$ $\dfrac{5^ {2021} -1}{4}$ Bình luận
Bạn tham khảo :
$C = 1+5+5^2+5^3+…+5^{2020}$
$5C = 5+5^2+5^3+5^4+ … +5^{2021}$
$5C -C = (5+5^2+5^3+5^4+ … +5^{2021}) -(1+5+5^2+5^3+…+5^{2020})$
$4C = 5^{2021} – 1$
$C = \dfrac{5^{2021} – 1}{4}$
$c=1+5+5^2 + 5 ^3 + …. + 5 ^ {2020}$
$5c = 5 + 5^2 + 5^3 + 5^4 +……..+ 5^ {2021}$
Ta lấy : $5c – c$
4c = $5^{2021}-1$
$c =$ $\dfrac{5^ {2021} -1}{4}$