tính tổng A=1/3+1/3mũ2+1/3mũ3+1/3mũ4+……+1/3mũ100

2 bình luận về “tính tổng A=1/3+1/3mũ2+1/3mũ3+1/3mũ4+……+1/3mũ100”

1. A = 1/3 + 1/(3^(2)) + 1/(3^(3)) + 1/(3^(4)) + … + 1/(3^(100))

   3A = 1 + 1/(3^(2)) + 1/(3^(3)) + … + 1/(3^(99))

   3A – A = ( 1/3 + 1/(3^(2)) + 1/(3^(3)) + 1/(3^(4)) + … + 1/(3^(100)) ) – ( 1 + 1/(3^(2)) + 1/(3^(3)) + … + 1/(3^(100)) )

   2A = 1 – 1/(3^(100))

   A = ( 1 – 1/(3^(100)) )/2

    

   Trả lời
2. A = 1/3 + 1/(3^2) + … + 1/(3^100)

   3A = 1 + 1/3 + … + 1/(3^99)

   3A – A = (1 + 1/3 + … + 1/(3^99) ) – ( 1/3 + 1/(3^2) + … + 1/(3^100) )

   2A = 1 – 1/(3^100)

   => A = ( 1 – 1/(3^100) )/2

   Trả lời