Question

MỌI NGƯỜI CÓ THỂ GIẢI GẤP CHO EM BÀI NÀY ĐƯỢC KO Ạ

TÍNH TỔNG M=1+3+3^2+3^3+.....+3^20+3^21

Answer 1

\(M=1+3+3^2+3^3+...+3^{20}+3^{21}\)

\(\implies 3M=3+3^2+3^3+3^4+...+3^{21}+3^{22}\)

\(\implies 3M-M=(3+3^2+3^3+3^4+...+3^{21}+3^{22})-(1+3+3^2+3^3+...+3^{20}+3^{21})\)

\(\implies 2M=3^{22}-1\)

\(\implies M=\frac{3^{22}-1}{2}\)

_Học tốt_

Answer 2

\(M=1+3+3^2+3^3+....+3^{20}+3^{21}\)

\(\Rightarrow3M=3+3^2+3^3+3^4+.....+3^{21}+3^{22}\)

\(\Rightarrow3M-M=\left(3+3^2+3^3+....+3^{22}\right)-\left(1+3+3^2+....+3^{21}\right)\)

\(\Rightarrow2M=3^{22}-1\)

\(\Rightarrow M=\frac{3^{22}-1}{2}\)

Answer 3

\(M=1+3+3^2+3^3+...+3^{20}+2^{21}\)

\(3M=3+3^2+3^3+3^4+...+3^{22}\)

\(2M=3^{22}-1\)

\(M=\frac{3^{22}-1}{2}\)

Answer 4

M=\(1+3+3^2+3^3+...+3^{20}+3^{21}\)

\(3M=1+3^2+3^3+..+3^{21}+3^{22}\)

\(3M-M=3^{22}-3\)

\(2M=3^{22}-3\)

\(M=\frac{3^{22}-3}{2}\)

Học tốt