Mình nghĩ đây là nâng cao tiểu học 
Đặt S = 1/2 + 1/4 + 1/8 + 1/16 + ... 
==> 2S = 1 + 1/2 + 1/4 + 1/8 + 1/16 + ... 
2S = 1 + S 
==> S = 1 
Đây cũng là kết quả khi tính theo cấp số nhân khi n --> vô cùng

2A=1+1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512

2A-A=1-1/1024

A=1-1/1024

A=1023/1024

\(=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{10}}\)

\(2A=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^9}\)

\(2A-A=1-\frac{1}{2^{10}}\)

\(\Rightarrow A=\frac{1}{2^{10}-1}\)\(=\frac{1}{1023}\)

nha

\(A=\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}+\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-....+\frac{1}{256}-\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{512}\)

\(=\frac{255}{512}\)

Vậy \(A=\frac{255}{512}\)

=1/2-1/4+1/4-1/8+1/8-....+1/156-1/152

=1/2-1/152

=255/512

A=255/512

\(A=\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}+\frac{1}{512}\)

\(A=\frac{2-1}{4}+\frac{2-1}{8}+\frac{2-1}{16}+\frac{2-1}{32}+\frac{2-1}{64}+\frac{2-1}{128}+\frac{2-1}{256}+\frac{2-1}{512}\)

\(A=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+...+\frac{1}{256}-\frac{1}{512}\)

\(A=\frac{1}{2}-\frac{1}{512}\)

\(A=\frac{256}{512}-\frac{1}{512}=\frac{255}{512}\)

\(A=\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}+\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+....+\frac{1}{256}-\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{512}\)

\(=\frac{255}{512}\)

Vậy \(A=\frac{255}{512}\)

A=14 +18 +116 +132 +164 +1128 +1256 +1512 

=12 −14 +14 −18 +....+1256 −1512 

=12 −1512 

=255512 

Vậy A=255512 

Phạm Long Khánh

A = 255/512

X x (1/2+1/4+1/8+1/16+1/32+1/64+1/128) = 127/128

X x 127/128                                            = 127/128

                                                        X   = 127/128 : 127/128

                                                        X   = 1

câu 1 : 

1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 = ( 1/2 + 1/4 ) + ( 1/8 + 1/16 ) + ( 1/32 + 1/64 ) + 1/128 

                                                                       = 3/4 + 3/16 + 3/64 + 1/128 

                                                                        = ( 3/4 + 3/16 ) + ( 3/64 + 1/128 ) 

                                                                       = 15/16 + 7/128 

                                                                        = 127/128

câu 2 :   tiền lãi 1 tháng là :

1 000 000 : 100 x 1 = 5000 ( đồng ) 

Vậy chọn câu a 

ĐS:...

cdowij chút mk thiếu , câu 1 chọn a lun nha

thank you bn nhìu nha

2

4

8

16

32

64

128

256

2

4

8

16

64

128

256

          k mk nhé

1+1=2

2+2=4

4+4=8

8+8=16

16+16=32

32+32=64

64+64=128

128+128=256

tk m nhé

b: A=1/3+1/9+...+1/3^10

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

=>A*2=1-1/3^10=(3^10-1)/3^10

=>A=(3^10-1)/(2*3^10)

c: C=3/2+3/8+3/32+3/128+3/512

=>4C=6+3/2+...+3/128

=>3C=6-3/512

=>C=1023/512

d: A=1/2+...+1/256

=>2A=1+1/2+...+1/128

=>A=1-1/256=255/256

C= \(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\)

2C = \(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}\)

2C-C = \(1-\dfrac{1}{128}\)

C= \(\dfrac{127}{128}\)

C= 12+14+18+116+132+164+112821​+41​+81​+161​+321​+641​+1281​

2C = 1+12+14+18+116+132+1641+21​+41​+81​+161​+321​+641​

2C-C = 1−11281−1281​

C= 127128128127​
 

A= 1/2 + 1/4+ 1/8+ 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512 
A = 1 - 1/2 + 1/2- 1/4 + 1/4 - 1/8 + 1/8 - 1/16 + 1/16 - 1/32 + 1/32 - 1/64 + 1/64 - 1/128 + 1/128 - 1/256 - 1/256 - 1/512 
A = 1 - 1/512 

Ủng hộ mk nha! ^_^