Question

Rut s gọn M:

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

Answer 1

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

\(2M=2\left(2+2^2+...+2^{20}\right)\)

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

\(2M-M=\left(2^2+2^3+...+2^{21}\right)-\left(2+2^2+...+2^{20}\right)\)

\(M=2^{21}-2\)

Answer 2

Giải:

M = 2 + 2² + 2³ + ... +2²⁰

2M = 2² + 2³ + 2⁴ + ... +2²¹

2M - M = (2² + 2³ + 2⁴ + ... + 2²¹) - (2 + 2² + 2³ + 2⁴+ ... + 2²⁰)

M = 2²¹ - 2.

Chúc bạn học tốt!