Nhanh lên giúp tớ

1413/160

49/5 + 1/2 - 1/4 - 1/8 - 1/16 - 1/32 = 1413/60 = 8,83125

1573/160 tính mệt ghê

1573/160

\(A=\dfrac{49}{5}-\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}\right)\)

\(A=\dfrac{49}{5}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{32}\right)\)

\(A=\dfrac{49}{5}-\left(1-\dfrac{1}{32}\right)=\text{​​}\dfrac{49}{5}-\dfrac{31}{32}\text{​​}\)

\(A=\dfrac{1413}{160}\text{​​}\)

Ta có : \(\frac{49}{5}-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}\)

\(=\frac{49}{5}-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)\)

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

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

=> \(2A-A=1-\frac{1}{32}\Rightarrow A=\frac{31}{32}\)

Vậy \(\frac{49}{5}-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}\)

\(=\frac{49}{5}-\frac{31}{32}=\frac{1413}{160}\)

\(\frac{49}{5}-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}\)\(=\)\(\frac{4189}{480}\)

tính nhanh 

49/5-1/2-1/4-1/8-1/16-1/32=8,83125

nha bn duyệt đi

\(\frac{49}{5}-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}=\frac{1413}{160}=8,83125\)

Tính các tổng sau:

1, S=1-2+3_4+..+25-26

S =-1+3-5+7-...-53+55                       ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)         ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

Á nhầm rùi xl bn nha

3 

S =-1+3-5+7-...-53+55     ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)      ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

a. \(\dfrac{17}{13}-\dfrac{14}{23}+\dfrac{9}{13}-\dfrac{9}{23}=\left(\dfrac{17}{13}+\dfrac{9}{13}\right)-\left(\dfrac{14}{23}+\dfrac{9}{23}\right)=\dfrac{26}{13}-\dfrac{23}{23}=2-1=1\)

b.\(\dfrac{49}{5}-\dfrac{1}{2}-\dfrac{1}{4}-\dfrac{1}{32}-\dfrac{1}{16}-\dfrac{1}{32}=\dfrac{49}{5}-\left(1-\dfrac{1}{32}\right)=\dfrac{44}{5}+\dfrac{1}{32}=\dfrac{1413}{160}\)

trong sách giáo khoa hả

hnay mik cg hc 

Bài 3: 

a: x+3/8=14/9x10/35

\(\Leftrightarrow x+\dfrac{3}{8}=\dfrac{4}{9}\)

=>x=4/9-3/8=32/72-27/72=5/72

b: \(x-\dfrac{2}{7}=\dfrac{21}{10}\cdot\dfrac{15}{28}=\dfrac{21}{28}\cdot\dfrac{15}{10}=\dfrac{3}{4}\cdot\dfrac{3}{2}=\dfrac{9}{8}\)

\(\Leftrightarrow x=\dfrac{9}{8}+\dfrac{2}{7}=\dfrac{63}{56}+\dfrac{16}{56}=\dfrac{79}{56}\)

c: \(\dfrac{11}{7}-x=\dfrac{8}{3}\cdot\dfrac{9}{32}=\dfrac{1}{4}\cdot3=\dfrac{3}{4}\)

nên \(x=\dfrac{11}{7}-\dfrac{3}{4}=\dfrac{44}{28}-\dfrac{21}{28}=\dfrac{23}{28}\)

d: \(x+\dfrac{2}{5}=\dfrac{12}{35}\cdot\dfrac{14}{9}=\dfrac{4}{3}\cdot\dfrac{2}{5}=\dfrac{8}{15}\)

nên \(x=\dfrac{8}{15}-\dfrac{2}{5}=\dfrac{8}{15}-\dfrac{10}{15}=-\dfrac{2}{15}\)