Question

Cho A= 3¹+3²+3³ + ..........+3²⁰¹⁶ Tìm x khi 2A+3=3^x

Answer 1

A=3^1+3^2+...+3^2016       (1)

3A=3^2+3^3+....+3^2017     (2)

TRỪ VẾ VỚI VẾ CỦA (2) CHO (1)

3A-A=(3^2+3^3+...+3^2017)-(3^1+3^2+...+3^2016)

2A=3^2017-3

2A+3=3^2017

TA CÓ 2A+3=3^x

=>x=2017

=>

Answer 2

\(A=3^1+3^2+3^3+...+3^{2016}\)

\(3A=3^2+3^3+3^4+...+3^{2017}\)

Answer 3

Tks mn nhìu

Answer 4

\(3A-A=\left(3^2+3^3+3^4+..+3^{2017}\right)-\left(3^1+3^2+3^3+..+3^{2016}\right)\)

\(2A=3^{2017}-3^1\)

\(2A+3=3^{2017}\)

\(=>x=2017\)

Vậy x =2017

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