Question

Cho S = \(1+3+3^2+3^3+3^4+.......+3^{99}\)

 

 

Answer 1

\(S=1+3+3^2+3^3+...+3^{99}\)

\(3S=3+3^2+3^3+...+3^{100}\)

\(3S-S=3+3^2+3^3+...+3^{100}-1-3-3^2-...-3^{99}\)

\(2S=3^{100}-1\)

\(S=\frac{3^{100}-1}{2}\)

Answer 2

\(3S=3.3^2+3^3+...+3^{100}\)

\(3S-S=3^{100}-1\)

\(S=\frac{3^{100}-1}{3}\)

Answer 3

thanks các bạn nhé