A=1/2+1/4+1/8+1/16+...(tổng có 10 số hạng)

Ta có:Số hang 1:1/2

         Số hạng 2:1/4=1/2*1/2

         Số hạng 3:1/8=1/2*1/2*1/2

................................

        =>Số hạng 10=1/2*1/2*1/2*...(có 10 thừa số)

                            =1/1024

 => A=1/2+1/4+1/8+1/16+...+1/512 +1/1024(x)

=>2A=1+1/2+1/4+1/8+...+1/256+1/512(xx)

Lấy (xx)-(x) ta có

2A-A=1-1/1024(giản ước hết các số hạng của x)

A=1023/1024

A=1023/1024

1023/1024

A = 1/2 + 1/4 + 1/8 + 1/16 + ... + 1/512 + 1/1024

A x 2 = 1 + 1/2 + 1/4 + 1/8 + 1/16 + ... + 1/512

A x 2 - A = 1 + 1/2 - 1/2+ 1/4 -1/4 + 1/8 -1/8 + 1/16 -1/16 + ... + 1/512 - 1/512 - 1/1024

A = 1 - 1/1024

A = 1023/1024

=1-1/1024=1023/1024

A = 1/2 + 1/4 + 1/8 + 1/16 + ... + 1/512 + 1/1024

A x 2 = 1 + 1/2 + 1/4 + 1/8 + 1/16 + ... + 1/512

A x 2 - A = 1 + 1/2 - 1/2+ 1/4 -1/4 + 1/8 -1/8 + 1/16 -1/16 + ... + 1/512 - 1/512 - 1/1024

A = 1 - 1/1024

A = 1023/1024

A = \(\frac{1}{2}\) + \(\frac{1}{4}\) +\(\frac{1}{8}\)+ \(\frac{1}{16}\)+.....

= (1 - \(\frac{1}{2}\)) + (\(\frac{1}{2}-\frac{1}{4}\) ) + (\(\frac{1}{4}-\frac{1}{8}\)) + ... + (\(\frac{1}{512}\) - \(\frac{1}{1024}\)).

= 1 - \(\frac{1}{1024}\)

= \(\frac{1023}{1024}\)

ĐS 1023/1024

\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{2^{10}}\)

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

\(\frac{1}{2}A=\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+...+\frac{1}{2^{11}}\)

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

\(A=\left(\frac{1}{2^{11}}-\frac{1}{2}\right):\frac{1}{2}=\left(\frac{1}{2^{11}}-\frac{1}{2}\right)\times2=\frac{2}{2^{11}}-\frac{2}{2}=\frac{1}{2^{10}}-1\)

A = 1/5130 nha bạn

a = 1/2+1/4+1/8+1/16

= (1 - 1/2) + (1/2 -1/4) + (1/4 - 1/8) + ... + (1/512 - 1/1024).

= 1 - 1/1024

= 1023/1024

bạn monoka sai rồi