Question

[Lê Nguyễn Khôi Nguyên]

Tính tổng sau

 B = 1 + 3¹ + 3² + ... + 3²⁰¹⁶

Answer 1

[Ng Ngọc]

\(B=1+3^1+3^2+...+3^{2016}\)

\(3B=3+3^2+3^3+3^4+...+3^{2017}\)

\(3B-B=3^{2017}-1\)

\(B=\dfrac{3^{2017}-1}{2}\)