1+5/4+5/8+5/16+5/32+5/64
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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
\(1+\frac{5}{4}+\frac{5}{8}+\frac{5}{16}+\frac{5}{32}+\frac{5}{64}\)
\(=\frac{64}{64}+\frac{80}{64}+\frac{40}{64}+\frac{20}{64}+\frac{10}{64}+\frac{5}{64}\)
\(=\frac{64+80+40+20+10+5}{64}\)
\(=\frac{219}{64}\)
\(=\frac{27}{8}\)
1+5/4+5/8+5/16+5/32+5/64
=1+5/4+5/8+5/16+5/32+5/64
=1+(5/4+5/8+5/16+5/32+5/64)
=1+[5x(1/4+1/8+1/16+1/32+1/64)]
A=1/4+1/8+1/16+1/32+1/64
2A=1/2+1/4+1/8+1/16+1/32
2A-A=(1/2+1/4+1/8+1/16+1/32)+(1/4+1/8+1/16+1/32+1/64)
A=1/2-1/64
A=31/64
1+[5x31/64]
=1+155/64
=219/64
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
Đặt \(A=1+\frac{5}{4}+\frac{5}{8}+\frac{5}{16}+\frac{5}{32}+\frac{5}{64}\)
\(=5\cdot\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)\)
Đặt \(B=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(\Rightarrow2\cdot B=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)
\(\Rightarrow B=2\cdot B-B=1-\frac{1}{64}=\frac{63}{64}\)
\(\Rightarrow A=5\cdot\frac{63}{64}=\frac{315}{64}\)
\(1+\dfrac{5}{4}+\dfrac{5}{8}\)\(+\) \(\dfrac{5}{16}+\dfrac{5}{32}+\dfrac{5}{64}\)
= \(\dfrac{64}{64}+\dfrac{80}{64}+\dfrac{40}{64}+\dfrac{20}{64}+\dfrac{10}{64}+\dfrac{5}{64}\)
= \(\dfrac{64+80+40+20+10+5}{64}\)
= \(\dfrac{219}{64}\)
= \(\dfrac{27}{8}\)
Sai