xin lỗi mk làm sai kết quả là 254

1+1+2+2+4+4+8+8+16+16+32+32+64+64=254

\(2xB=1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}\)

\(B=2xB-B=1-\dfrac{1}{64}=\dfrac{63}{64}\)

63/64

1/2      +       1/4      +      1/8        +     1/16        +       1/32         +      1/64

= 1 – 1/2  +  1/2 - 1/4  +  1/4 - 1/8  +  1/8 - 1/16  +  1/16 - 1/32  +  1/32 - 1/64

= 1 – 1/64

= 63/64

Bên trên mik trình bày như vậy cho bạn dễ nhìn nha!

quy đồng mẫu số thành 64 rồi cộng.

1/2+1/4+1/8+1/16+1/32+1/64=32/64+16/64+8/64+2/64+1/64=59/64 

Chúc bạn học tốt

để công ta chuyển các mẫu số lớn thành các mẫu số chung nhỏ nhất

ta co

1/2+1/2+1/2+1/2+1/2+1/2

=1/4+1/4+1/4

=1/12

Đặt \(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)

\(\Rightarrow2A=2\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)\)

\(\Rightarrow2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)

\(\Rightarrow2A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)\)

\(\Rightarrow A=1-\frac{1}{64}\)

\(\Rightarrow A=\frac{64}{64}-\frac{1}{64}\)

\(\Rightarrow A=\frac{63}{64}\)

\(2A=1+\dfrac{1}{2}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}\)

\(2A-A=\left(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{18}+\dfrac{1}{32}\right)-\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}\right)\)

\(A=1-\dfrac{1}{64}\)

\(A=\dfrac{63}{64}\)

giúp em với ạ , em cấn gấp ,  4h em học rồi ạ . Cảm ơn những ai giúp em ạ , em tick luôn ạ

Đặt A = 1 + 1/2 + 1/4 + ... + 1/64

2A = 1 + 1/2 + 1/4 + ... + 1/32

2A - A = ( 1 + 1/2 + ... + 1/32 ) - ( 1 + 1/2 + ... + 1/64 )

A = 1 - 1/64

A = 63/64

C= \(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\)

2C = \(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}\)

2C-C = \(1-\dfrac{1}{128}\)

C= \(\dfrac{127}{128}\)

C= $\genfrac{}{}{0ex}{}{1}{2}+\genfrac{}{}{0ex}{}{1}{4}+\genfrac{}{}{0ex}{}{1}{8}+\genfrac{}{}{0ex}{}{1}{16}+\genfrac{}{}{0ex}{}{1}{32}+\genfrac{}{}{0ex}{}{1}{64}+\genfrac{}{}{0ex}{}{1}{128}$

2C = $1+\genfrac{}{}{0ex}{}{1}{2}+\genfrac{}{}{0ex}{}{1}{4}+\genfrac{}{}{0ex}{}{1}{8}+\genfrac{}{}{0ex}{}{1}{16}+\genfrac{}{}{0ex}{}{1}{32}+\genfrac{}{}{0ex}{}{1}{64}$

2C-C = $1-\genfrac{}{}{0ex}{}{1}{128}$

C= $\genfrac{}{}{0ex}{}{127}{128}$