Question

[đỗ bảo trâm]

1+1/3 + 1/9 + 1/27 + 1/81 + 1/243=?

mik xl ạ hồi trưa mik ghi sai đề bài mong đc giải

Answer 1

[Vũ Quang Huy]

1+1/3 + 1/9 + 1/27 + 1/81 + 1/243

=243/243+81/243+27/243 +3/243 +1/243

=\(\dfrac{243+81+27+3+1}{243}\)

=355/243

Answer 2

[Akai Haruma]

Lời giải:

$A=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}$

$3A=3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}$

$3A-A=3-\frac{1}{243}$

$2A=\frac{728}{243}$

$A=\frac{364}{243}$