Đặt A=\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+................+\frac{1}{2048}+\frac{1}{4096}\)

2A=\(1+\frac{1}{2}+\frac{1}{4}+....................+\frac{1}{1024}+\frac{1}{2048}\)

2A-A=\(\left(1+\frac{1}{2}+\frac{1}{4}+................+\frac{1}{1024}+\frac{1}{2048}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...............+\frac{1}{2048}+\frac{1}{4096}\right)\)

A=\(1-\frac{1}{4096}\)

A=\(\frac{4095}{4096}\)

4095/4096 đó lam lợn hả

các bạn sai rồi bằng 2047/2048 đó chắc chắn 100% luôn mk thi rồi.

Đúng thì nhớ k nha các bạn hihi ^-^

A = 1/2+1/4+...+1/2048

2A= 1+ 1/2+ 1/4+...+1/1024

2A-A= ( 1+ 1/2+...+1/1024 ) -  (1/2+1/4+...+2048)

A= 1- 1/2048

A= 2047/2048

Từ biểu thức trên ta được

A=1/2+1/2^2+1/2^3+....+1/2^11+1/2^12

2A-A=2(1/2+1/2^2+1/2^3+....+1/2^11+1/2^12)-(1/2+1/2^2+1/2^3+....+1/2^11+1/2^12)

A=1+1/2^2+1/2^3+....+1/2^11-1/2-1/2^2-...-1/2^12

A=1/2-1/2^12

Ủng hộ cho mình nha bạn

\(A=\)\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}+\frac{1}{2048}+\frac{1}{4096}\)

\(A=\)\(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{12}}\)

\(2A=\)\(2\left(\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{12}}\right)\)

\(2A=\)\(1+\frac{1}{2}+...+\frac{1}{2^{11}}\)

\(2A-A=\)\(\left(1+\frac{1}{2}+...+\frac{1}{2^{11}}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{12}}\right)\)

\(A=1-\frac{1}{2^{12}}\)

Đặt \(A=1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-..-\frac{1}{2048}\)

\(\Rightarrow A=1-\left(1-\frac{1}{2}\right)-\left(\frac{1}{2}-\frac{1}{4}\right)-..-\left(\frac{1}{1024}-\frac{1}{2048}\right)\)

\(\Rightarrow A=1-1+\frac{1}{2}-\frac{1}{2}+\frac{1}{4}-..-\frac{1}{1024}+\frac{1}{2018}\)

\(\Rightarrow A+\frac{1}{2018}\)

1-1/2-1/4-1/8-1/16-1/32-1/64-1/128-1/256-1/512-1/1024-1/2048 =0.00048828125

Nhân cả hai vế với 3-1, ta được:
(3-1)A=(3+1)(3-1)(3^2+1)...(3^2048+1)
(3-1)A=(3^2-1)(3^2+1)....(3^2048+1)
........
(3-1)A=(3^2048-1)(3^2048+1)
(3-1)A=3^4096-1=> A=\(\frac{3^{4096}-1}{3-1}\)
(Nếu có thể thu gọn tiếp thì bạn cứ thế mà tính)

1+1=2

2+2=4

4+4=8

8+8=16

16+16=32

32+32=64

64+64=128

128+128 = 256

256+256=512

512+512= 1024

1024+1024 = 2048 

2048 + 2048 = 4096

1+1=2

2+2=4

4+4=8

8+8=16

16+16=32

32+32=64

64+64=128

128+128=256

256+256=512

512+512=1024

1024+1024=2048

2048+2048=4096

1+1=2

2+2=4

4+4=8

8+8=16

16+16=32

32+32=64

64+64=128

128+128=256

256+256=512

512+512=1024

1024+1024=2048

2048+2048=4096