Question

Tính giúp mình nha !

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

Answer 1

3A = 3 * ( 1/3+1/3^2+...+1/3^100)

= 1+1/3+1/3^2+...+1/3^99

3A-A=(1/3+1/3^2+..+1/3^100)-(1+1/3+...+1/3^99)

2A=1/3^100-1

A=(1/3^100-1)/2 

Answer 2

bạn Đỗ Linh Chi làm sai bét

   3A = 1 + 1/3 + 1/3^2  + ..... + 1/3^99

   3A - A =1 - 1/3^100

   2A = 1 - 1/3^100 = 3^100 - 1/3^100

   A = 3^100 - 1/2-3^100