Question

\(1+\frac{1}{3^2}+\frac{1}{3^4}+......+\frac{1}{3^{100}}\).Biết 8A=9-\(\frac{1}{3^n}\)

Vậy n=?

Answer 1

A=1+1/3^2+1/3^4+...+1/3^100

=>3^2.A=9+1/3+/3^2+...+1/3^98

=>9A-A=(9+1/3+1/3^2+...+1/3^98)-(1+1/3^2+1/3^4+...+1/3^100)

=>8A=9-1/3^100=9-1/3^n

=>1/3^100=1/3^n

=>3^100=3^n

=>n=100

Vậy n=100

Answer 2

Ban nguyen thieu cong thanh dung roi.ket qua bang 100

Answer 3

n= 100