Question

[Yuuki Asuna]

Viết tổng sau dưới dạng luỹ thừa cua 2:

A=2^{2 +} 2³ + 2^{4  +} .… + 2 ²⁰¹⁸

Answer 1

[_ℛℴ✘_]

\(A=2^2+2^3+...+2^{2018}\)

\(2A=2^3+2^4+...+2^{2019}\)

\(2A-A=\left(2^3+2^4+...+2^{2019}\right)-\left(2^2+2^3+...+2^{2018}\right)\)

\(A=2^{2019}-2^2\)

HOK TỐT .

Answer 2

[Nguyễn Thanh Hiền]

\(A=2^2+2^3+2^4+...+2^{2018}\)

\(\Rightarrow2A=2^3+2^4+2^5+...+2^{2019}\)

\(\Rightarrow2A-A=\left(2^3+2^4+2^5+...+2^{2019}\right)-\left(2^2+2^3+2^4+...+2^{2018}\right)\)

\(\Rightarrow A=2^{2019}-2^2\)

Vậy  \(A=2^{2019}-2^2\)

_Chúc bạn học tốt_