Question

Câu 1: Cho A = 1+2+2²+2³+...+2²⁰⁰. Tìm A.

Answer 1

A=1+2+2²+2³+...+2²⁰⁰

2A=2+2²+2³+2⁴+...+2²⁰¹

2A-A=(2+2²+2³+2⁴+...+2²⁰¹)-(1+2+2²+2³+...+2²⁰⁰)

A=2²⁰¹-1

Answer 2

\(A=1+2+2^2+2^3+...+2^{200}\)

=> \(2A=2+2^2+2^3+2^4+...+2^{201}\)

=> \(2A-A=2+2^2+2^3+2^4+...+2^{201}-\left(1+2+2^2+2^3+...+2^{200}\right)\)

=> \(A=2^{201}-1\)