S=3/2+5/4+9/8+....+257/256+513/512
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=1+\dfrac{1}{2}+1+\dfrac{1}{4}+1+\dfrac{1}{8}+...+1+\dfrac{1}{256}+1+\dfrac{1}{512}=\)
\(=1x\left(\dfrac{512-2}{2}+1\right)+\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{...1}{256}+\dfrac{1}{512}\right)=\)
\(256+B\)
\(2B=1+\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{512}+\dfrac{1}{1024}\)
\(B=2B-B=1+\dfrac{1}{1024}\)
\(\Rightarrow A=265+1+\dfrac{1}{1024}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1/ 2 + 2 = 4
2/ 4 + 4 = 8
3/ 8 + 8 = 16
4/ 16 + 16 = 32
5/ 32 + 32 =64
6/ 64 + 64 =128
7/ 128 + 128 =256
8/ 256 + 256 =512
9/ 521 + 512 =1033
10/ 2048 + 2048 =4096
![](https://rs.olm.vn/images/avt/0.png?1311)
1/2 + 1/4+ 1/8+ 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512
= 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
= 1 – 1/512
= 511/512 .
1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512 + 1/1024
Ta có :
1/512 = 1×2 / 512×2 = 2/1024
1/256 = 1×4 / 256×4 = 4/1024
1/128 = 1×8 / 128×8 = 8/1024
1/64 = 1×16 / 64×16 = 16/1024
1/32 = 1×32 / 32×32 = 32/1024
1/16 = 1×64 / 16×64 = 64/1024
1/8 = 1×128 / 8×128 = 128/1024
1/4 = 1×256 / 4×256 = 256/1024
1/2 = 1×512 / 2×512 = 512/1024
___________________________
=>
1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512 + 1/1024
= 512/1024 + 256/1024 + 128/1024 + 64/1024 + 32/1024 + 16/1024 + 8/1024 + 4/1024 + 2/1024 + 1/1024
= (512 + 256 + 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1) / 1024
= 1023/1024
![](https://rs.olm.vn/images/avt/0.png?1311)
A=1/2+1/4+1/8.....+1/256+1/512
2A=1+1/2+1/4+1/8...1/256
A=(1+1/2+1/4+1/8...1/256)-(1/2+1/4+1/8.....+1/256+1/512)
A=1-1/512
A=511/512
511/512
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 1+2+4+8+16+32+...+256+512+1024
= 20+21+22+23+24+25+...+28+29+210
= 1 + 2 + 22+3+4+5+...+8+9+10
= 3+254
![](https://rs.olm.vn/images/avt/0.png?1311)
Các số là :
(512 + 1 ) : 1 + 1 = 512 (so )
Tổng trên là :
(512 - 1 ) .512 : 2= 130816
Vậy tổng trên bằng 130816
![](https://rs.olm.vn/images/avt/0.png?1311)
2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 + 512
= 2 x 1 + 2 x 2 + 2 x 4 + 2 x 8 + 2 x 16 + 2 x 32 + 2 x 64 + 2 x 128 + 2 x 256
= 2 x ( 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 )
= 2 x 511
= 1022
![](https://rs.olm.vn/images/avt/0.png?1311)
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
1+1=2
2+2=4
4+4=8
8+8=16
16+16=32
32+32=64
64+64=128
128+128=265
256+256=512
512+512=1024
1024+1024=2048
Học tốt ^_^