Question

tim so tu nhien n,biet:

A=3+3²+3³+...+3¹⁰⁰ va 2A+B=3ⁿ

Answer 1

 

A = 3 + 3² + 3³ + ... + 3¹⁰⁰

3A = 3² + 3³ + 3⁴ + ... + 3¹⁰¹

3A - A = 3¹⁰¹ - 3

2A = 3¹⁰¹ - 3

Ta có: 

2A + 3 = 3ⁿ

3¹⁰¹ - 3 +3 = 3ⁿ

3¹⁰¹ = 3ⁿ

=> n = 101 

Vậy n = 101 

Answer 2

3A = 3²+3³+3⁴+...+3¹⁰¹

3A-A= 3¹⁰¹-3=2A

2A+3=3¹⁰¹-3+3=3ⁿ

^=>n=101