A=1/2+1/4+1/8+1/16+...+1/2048
2A=1+1/2+1/4+1/1/8+...+1/1024
2A-A=(1+1/2+...+1/1024)-(1/2+1/4+...+1/2048)
A=1-1/2048
A=2047/2048
Gọi biểu thức trên là A
A=1/2+1/2^2+1/2^3+....+1/2^10+1/2^11
2A=1+1/2+1/2^2+...+1/2^11+1/2^12
2A-A=1/2^12+1
A=1/2^12+1
(1981 x 1982 - 990) : (1980 x 1982 + 992)
=(1980 x 1982+1982 -990) : (1980 x 1982 +992)
=(1980 x 1982 + 992) : ( 1980 x 1982 + 992)
=1
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}+\frac{1}{2048}\)
\(A=\frac{1}{2^1}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{10}}+\frac{1}{2^{11}}\)
\(\Rightarrow2A=\frac{1}{2^0}+\frac{1}{2^1}+\frac{1}{2^2}+...+\frac{1}{2^9}+\frac{1}{2^{10}}\)
\(\Rightarrow2A-A=\frac{1}{2^0}+\frac{1}{2^1}+\frac{1}{2^2}+...+\frac{1}{2^9}+\frac{1}{2^{10}}-\frac{1}{2^1}-\frac{1}{2^2}-\frac{1}{2^3}-...-\frac{1}{2^{10}}-\frac{1}{2^{11}}\)
\(\Rightarrow A=\frac{1}{2^0}+\frac{1}{2^1}-\frac{1}{2^1}+\frac{1}{2^2}-\frac{1}{2^2}+\frac{1}{2^3}-\frac{1}{2^3}...+\frac{1}{2^{10}}-\frac{1}{2^{10}}-\frac{1}{2^{11}}\)
\(\Rightarrow A=\frac{1}{1}+0+0+...+0-\frac{1}{2^{11}}\)
\(\Rightarrow A=1-\frac{1}{2^{11}}\)\(A=1-\frac{1}{2^{11}}\)
Vậy
trả lời bằng 1 chúc bn hc giỏi
Sỹ
đáp số là 1 nha bạn
bang 1
hoctot nhe ban ok
