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[maicoi_hd2002]

[TẶNG BẠN] TRỌN BỘ Bí kíp học tốt 08 môn
Chắc suất Đại học top - Giữ chỗ ngay!!

ĐĂNG BÀI NGAY để cùng trao đổi với các thành viên siêu nhiệt tình & dễ thương trên diễn đàn.

1) tính tổng
$\dfrac{2}{5} + \dfrac{3}{6} + \dfrac{4}{7}$

2) Tính nhanh
a) $\dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32} +\dfrac{1}{64}$
b) $1 + \dfrac{1}{2} +\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}$

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[ngocphuong23]

2) tính nhanh
a) 1 phần 2 + 1 phần 4 + 1 phần 8 + 1 phần 16 +1 phần 32 + 1 phần 64

2)
a) $\dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32} +\dfrac{1}{64}$
= $2.(\dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32} +\dfrac{1}{64}$) - ($\dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32} +\dfrac{1}{64}$)
= ($1 + \dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32}$) - ($\dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16} + \dfrac{1}{32} +\dfrac{1}{64}$)
= $1 - \dfrac{1}{64}$
= $\dfrac{63}{64}$

 

[thieukhang61]

1 + \dfrac{1}{2} +\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}


Bạn thiếu phân số [TEX]\frac{1}{16}[/TEX] nhé!
Gọi tổng trên là A, ta có:
[TEX]A=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+\dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}+\frac{1}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{2}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{64}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{2}{64}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{32}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{2}{32}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{16}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{2}{16}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{8}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{2}{8}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{4}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{2}{4}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{2}[/TEX]
[TEX]A+\frac{1}{128}=1+1[/TEX]
[TEX]A=2-\frac{1}{128}[/TEX]
[TEX]A=1\frac{127}{128}[/TEX]

 

[hiennguyenthu082]

1 + \dfrac{1}{2} +\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}


Bạn thiếu phân số [TEX]\frac{1}{16}[/TEX] nhé!
Gọi tổng trên là A, ta có:
[TEX]A=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+\dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}+\frac{1}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{2}{128}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{64}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{2}{64}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{32}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{2}{32}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{16}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{2}{16}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{8}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{2}{8}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{4}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{2}{4}[/TEX]
[TEX]A+\frac{1}{128}=1+\frac{1}{2}+\dfrac{1}{2}[/TEX]
[TEX]A+\frac{1}{128}=1+1[/TEX]
[TEX]A=2-\frac{1}{128}[/TEX]
[TEX]A=1\frac{127}{128}[/TEX]

Gọi tổng trên là A, ta có:
$A=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+\dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \frac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{128}+\dfrac{1}{128}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{2}{128}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{64} + \dfrac{1}{64}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{1}{32} +\dfrac{2}{64}$

$A+\dfrac{1}{128}=1+\frac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{1}{32} +\dfrac{1}{32}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{2}{32}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{16}+ \dfrac{1}{16}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{2}{16}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{8} + \dfrac{1}{8}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{2}{8}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{4} + \dfrac{1}{4}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{2}{4}$

$A+\dfrac{1}{128}=1+\dfrac{1}{2}+\dfrac{1}{2}$

$A+\dfrac{1}{128}=1+1$

$A=2-\dfrac{1}{128}$

$A=1\dfrac{127}{128}$

 

[tayhd20022001]

Bài 1:
$\dfrac{2}{5}$+$\dfrac{3}{6}$+$\dfrac{4}{7}$
=$\dfrac{12}{30}$+$\dfrac{15}{30}$+$\dfrac{4}{7}$
=$\dfrac{27}{30}$+$\dfrac{4}{7}$
=$\dfrac{103}{70}$