Question

Các bạn ơi cho mình hỏi xíu, có làm được câu này ko?

A= 2¹ + 2² + 2³ +......+ 2³⁹ + 2⁴⁰

 

Answer 1

`A = 2^1 + 2^2 + 2^3 + ... + 2^39 + 2^40`

`2A = 2^2 + 2^3 + 2^4 + ... + 2^40 + 2^41`

`2A - A= (2^2 + 2^3 + 2^4 + ... + 2^40 + 2^41) - (2^1 + 2^2 + 2^3 + ... + 2^39 + 2^40)`

`A = 2^41 - 2`

Answer 2

`A= 2^1 + 2^2+ 2^3+...+2^39+ 2^40`

`2A= 2^2 + 2^3+ 2^4+...+ 2^40 + 2^41`

`2A-A= (2^2+2^3+2^4+...+2^40 +2^41)-(2^1+2^2+2^3+..+2^39+2^40)`

`A= 2^41-2`

Answer 3

\(A=2^1+2^2+2^3+...+2^{39}+2^{40}\\ 2^1A=2^2+2^3+2^4+...+2^{40}+2^{41}\\ \)

\(2^1A-A=A=\left(2^2+2^3+2^4+...+2^{40}+2^{41}\right)-\left(2^1+2^2+2^3+...+2^{40}+2^{41}\right)\\ A=2^{41}-2^1\)