Giải:

A=5/9+2/15-6/9

   =(5/9-6/9)+2/15

   = -1/9 + 2/15

   = 1/45

B=2/7-3/8+4/7+1/7-5/8+5/15

   = (2/7+4/7+1/7) + (-3/8-5/8) +1/3

   = 1+ (-1) +1/3

   =1/3

C=3/5+1/15+1/57+1/3-2/9-3/4-1/36

   =9/15+1/15+1/57+19/57-8/36-27/36-1/36

   =(9/15+1/15)+(1/57+19/57)+(-8/36-27/36-1/36)

   =2/3+20/57+(-1)

   =58/57+(-1)

   =1/57

D=1/1.2+1/2.3+1/3.4+...+1/99.100

   =1/1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100

   =1/1-1/100

   =99/100

Câu E mình ko biết làm nhé!

a: \(\dfrac{11}{4}+\left(-\dfrac{3}{5}+\dfrac{1}{3}\right):\dfrac{-4}{9}\)

\(=\dfrac{11}{4}+\dfrac{-9+5}{15}\cdot\dfrac{9}{-4}\)

\(=\dfrac{11}{4}+\dfrac{-4}{15}\cdot\dfrac{9}{-4}\)

\(=\dfrac{11}{4}+\dfrac{3}{5}=\dfrac{55+12}{20}=\dfrac{67}{20}\)

b: \(\dfrac{2}{6}-\left(-\dfrac{3}{3}+\dfrac{4}{7}\right):\dfrac{-9}{5}\)

\(=\dfrac{2}{6}-\left(-1+\dfrac{4}{7}\right)\cdot\dfrac{-5}{9}\)

\(=\dfrac{2}{6}-\dfrac{-3}{7}\cdot\dfrac{-5}{9}\)

\(=\dfrac{1}{3}-\dfrac{15}{63}\)

\(=\dfrac{6}{63}=\dfrac{2}{21}\)

c: \(21-\dfrac{15}{4}:\left(\dfrac{3}{8}-\dfrac{1}{6}\right)\)

\(=21-\dfrac{15}{4}:\dfrac{3\cdot3-4}{24}\)

\(=21-\dfrac{15}{4}\cdot\dfrac{24}{5}\)

\(=21-3\cdot6=3\)

\(a.\dfrac{11}{4}+\left(-\dfrac{3}{5}+\dfrac{1}{3}\right):-\dfrac{4}{9}\)

\(=\dfrac{11}{4}+\left(-\dfrac{4}{15}\right):-\dfrac{4}{9}\)

\(=\dfrac{11}{4}+\dfrac{3}{5}=\dfrac{67}{20}\)

\(b.\dfrac{2}{6}-\left(-\dfrac{3}{3}+\dfrac{4}{7}\right):-\dfrac{9}{5}\)

\(=\dfrac{2}{6}-\left(-\dfrac{3}{7}\right):-\dfrac{9}{5}\)

\(=\dfrac{2}{6}-\dfrac{5}{21}=\dfrac{2}{21}\)

\(c.21-\dfrac{15}{4}:\left(\dfrac{3}{8}-\dfrac{1}{6}\right)\)

\(=21-\dfrac{15}{4}:\dfrac{5}{24}\)

\(=21-18=3\)

lệnh for...to...do:

a)program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  for i:=1 to 9 do s:=s+i;

  write(s);

readln;

end.

b)

program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  for i:=1 to 14 do

begin

if i mod 2=0 then

s:=s+i;

end;

  write(s);

readln;

end.

c)

program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  for i:=1 to 15 do

begin

if i mod 2=1 then

s:=s+i;

end;

  write(s);

readln;

end.

lệnh while...do

a)program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  i:=1;

while i<=9 do

begin

  s:=s+i;

i:=i+1;

end;

  write(s);

readln;

end.

b)program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  i:=1;

while i<=14 do

begin

if i mod 2=0 then

  s:=s+i

else i:=i+1;

end;

  write(s);

readln;

end.

c)

program tinh_tong;

uses crt;

var i,s:byte;

begin

  clrscr;

  s:=0;

  i:=1;

while i<=15 do

begin

if i mod 2=1 then

  s:=s+i

else i:=i+1;

end;

  write(s);

readln;

end.

cách giải bài này như nào: 5/20+1/4+6/24+8/32=bao nhiêu

    \(\dfrac{4}{5}\) : (\(\dfrac{4}{5}\) .- \(\dfrac{5}{4}\)) : (\(\dfrac{16}{25}\) - \(\dfrac{1}{5}\))

=  \(\dfrac{4}{5}\) : (-1) : (\(\dfrac{16}{25}\) - \(\dfrac{5}{25}\))

= -\(\dfrac{4}{5}\)  : \(\dfrac{11}{25}\)

= - \(\dfrac{4}{5}\) x \(\dfrac{25}{11}\)

=  - \(\dfrac{20}{11}\)

    \(\dfrac{11}{12}\) : (\(\dfrac{7}{9}\) + \(\dfrac{-1}{3}\)) - (\(\dfrac{2}{3}\) - \(\dfrac{5}{15}\))

= \(\dfrac{11}{12}\) : (\(\dfrac{7}{9}\) - \(\dfrac{3}{9}\)) - (\(\dfrac{2}{3}\) - \(\dfrac{1}{3}\))

= \(\dfrac{11}{12}\) : \(\dfrac{4}{9}\) - \(\dfrac{1}{3}\)

= \(\dfrac{11}{12}\) x \(\dfrac{9}{4}\) - \(\dfrac{1}{3}\)

= \(\dfrac{99}{48}\) - \(\dfrac{1}{3}\)

= \(\dfrac{99}{48}\) - \(\dfrac{16}{48}\)

= \(\dfrac{83}{48}\)  

\(\dfrac{4}{5}\): (\(\dfrac{4}{5}\).-\(\dfrac{5}{4}\)) : (\(\dfrac{16}{25}\) - \(\dfrac{1}{5}\))

=\(\dfrac{4}{5}\) x - 1: (\(\dfrac{16}{25}\) - \(\dfrac{5}{25}\))

= - \(\dfrac{4}{5}\) : \(\dfrac{11}{25}\)

= - \(\dfrac{4}{5}\) x \(\dfrac{25}{11}\)

= - \(\dfrac{20}{11}\) 

\(\dfrac{11}{12}\): (\(\dfrac{7}{9}\) + - \(\dfrac{1}{3}\)) - (\(\dfrac{2}{3}\) - \(\dfrac{5}{15}\))

= \(\dfrac{11}{12}\) : (\(\dfrac{7}{9}\) - \(\dfrac{3}{9}\)) - (\(\dfrac{2}{3}\) - \(\dfrac{1}{3}\))

= \(\dfrac{11}{12}\) : \(\dfrac{4}{9}\) - \(\dfrac{1}{3}\)

= \(\dfrac{11}{12}\) x \(\dfrac{9}{4}\) - \(\dfrac{1}{3}\)

= \(\dfrac{99}{48}\) - \(\dfrac{16}{48}\)

= \(\dfrac{83}{48}\) 

- \(\dfrac{2}{5}\).(\(\dfrac{9}{8}\) + \(\dfrac{16}{32}\) - \(\dfrac{3}{4}\)) - \(\dfrac{9}{10}\)

= - \(\dfrac{2}{5}\).(\(\dfrac{9}{8}\) + \(\dfrac{4}{8}\) - \(\dfrac{6}{8}\)) - \(\dfrac{9}{10}\)

= - \(\dfrac{2}{5}\).(\(\dfrac{13}{8}\) - \(\dfrac{6}{8}\)) - \(\dfrac{9}{10}\)

= - \(\dfrac{2}{5}\).\(\dfrac{7}{8}\) - \(\dfrac{9}{10}\)

= - \(\dfrac{7}{20}\) - \(\dfrac{18}{20}\)

= - \(\dfrac{5}{4}\)

a)\(=\dfrac{16}{13}-\dfrac{3}{15}+\dfrac{6}{13}=\dfrac{22}{13}-\dfrac{3}{15}=\dfrac{96}{65}\)

b)\(=\dfrac{21}{8}-\left(\dfrac{5}{10}+\dfrac{6}{10}\right)=\dfrac{21}{8}-\dfrac{11}{10}=\dfrac{61}{40}\)

c)\(=\dfrac{27}{10}-3-\dfrac{4}{7}--\dfrac{61}{70}\)

d)\(=\dfrac{576}{702}=\dfrac{4}{5}\)

e)\(=\left(\dfrac{20}{15}-\dfrac{12}{15}\right)\times\dfrac{25}{2}=\dfrac{8}{15}\times\dfrac{25}{2}=\dfrac{20}{3}\)

f)\(=\dfrac{24}{12}-\dfrac{4}{12}-\dfrac{6}{12}-\dfrac{2}{12}-\dfrac{3}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

d) \(=\dfrac{32}{45}x\dfrac{18}{16}=\dfrac{576}{720}=\dfrac{115}{114}\)

e) \(=\left(\dfrac{4}{3}-\dfrac{4}{5}\right)x\dfrac{25}{12}=\dfrac{8}{15}x\dfrac{25}{12}=\dfrac{200}{180}=\dfrac{10}{9}\)

f) \(=\dfrac{2}{1}-\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{1}{6}-\dfrac{3}{12}=\dfrac{24}{12}-\dfrac{4}{12}-\dfrac{6}{12}-\dfrac{2}{12}-\dfrac{3}{12}\)

\(=\dfrac{20}{12}-\dfrac{4}{12}-\dfrac{3}{12}=\dfrac{16}{12}-\dfrac{3}{12}=\dfrac{13}{12}\)

Làm 1 câu

10/3...>...1/3

Mấy câu ssu tự quy đồng hay gì gì đấy!

10/3.>..1/3.     10/6.>..3/8.     17/4.>..5/6.    1/3..<.5/9     5/8.<..7/5    3/4..<.15/6      10/9.>..10/11   7/8..<.7/2       15/9.>..3/8  15/7.>..15/8      16/5.>..16/7    25/11..<.1

3.... + .....2 = 86 số thích hợp điền vảo chỗ chấm là

a 7/15 + (5/6 - 1/3) = 7/15 + 1/2 = 14/30 + 15/30 = 29/30

b 4/7 *21/16 : 5/8 = 3/4  : 5/8 = 6/5

c 15/8 - 4/9 * 6/8+ 1/6 =15/8 - 1/3 + 1/6 = 37/24 + 1/6 = 41/24

d 5/12+(3/4 + 2/3 ) : 34/3 =

a/\(\frac{7}{15}+\left(\frac{5}{6}-\frac{1}{3}\right)=\frac{7}{15}+\frac{1}{2}=\frac{29}{30}\)

b/\(\frac{4}{7}\cdot\frac{21}{16}:\frac{5}{8}=\frac{4}{7}\cdot\frac{2}{16}\cdot\frac{8}{5}=\frac{4}{35}\)

c/\(\frac{15}{8}-\frac{4}{9}\cdot\frac{6}{8}+\frac{1}{6}=\frac{15}{8}-\frac{1}{3}+\frac{1}{6}=\frac{41}{24}\)

d/ \(\frac{5}{12}+\left(\frac{3}{4}+\frac{2}{3}\right):\frac{34}{3}=\frac{5}{12}+\frac{17}{12}:\frac{34}{3}=\frac{5}{12}+\frac{1}{8}=\frac{13}{24}\)

a/   \(\frac{7}{15}+\left(\frac{5}{6}-\frac{1}{3}\right)\)

= \(\frac{7}{15}+\frac{1}{2}\)

= \(\frac{29}{30}\)

b/ \(\frac{4}{7}.\frac{21}{16}:\frac{5}{8}\)

= \(\frac{4}{7}.\frac{21}{16}.\frac{8}{5}\)

= \(\frac{6}{5}\)

c/ \(\frac{15}{8}-\frac{4}{9}.\frac{6}{8}+\frac{1}{6}\)

= \(\frac{15}{8}-\frac{1}{3}+\frac{1}{6}\)

= \(\frac{41}{24}\)

d/ \(\frac{5}{12}+\left(\frac{3}{4}+\frac{2}{3}\right):\frac{34}{3}\)

= \(\frac{5}{12}+\frac{17}{12}\)\(:\frac{34}{3}\)

= \(\frac{5}{12}+\frac{1}{8}\)

= \(\frac{13}{24}\)

a) \(\dfrac{21}{15}\) + \(\dfrac{2}{5}\) = \(\dfrac{9}{5}\)
b)  \(\dfrac{6}{16}\) + \(\dfrac{1}{8}\) = \(\dfrac{1}{2}\)

c)  \(\dfrac{3}{12}\) + \(\dfrac{3}{4}\) = 1

a) \(2+\dfrac{3}{4}\)

\(=\dfrac{8}{4}+\dfrac{3}{4}\)

\(=\dfrac{8+3}{4}\)

\(=\dfrac{11}{4}\)

b) \(\dfrac{1}{3}+\dfrac{3}{2}-\dfrac{7}{4}\)

\(=\dfrac{4}{12}+\dfrac{18}{12}-\dfrac{21}{12}\)

\(=\dfrac{4+18-21}{12}\)

\(=\dfrac{1}{12}\)

c) \(\dfrac{1}{6}+\dfrac{3}{8}-\dfrac{1}{4}\)

\(=\dfrac{4}{24}+\dfrac{9}{24}-\dfrac{6}{24}\)

\(=\dfrac{4+9-6}{24}\)

\(=\dfrac{7}{24}\)

d) \(\dfrac{5}{12}+\dfrac{3}{8}\times\dfrac{4}{9}\)

\(=\dfrac{5}{12}+\dfrac{3\times4}{8\times9}\)

\(=\dfrac{5}{12}+\dfrac{1}{6}\)

\(=\dfrac{5}{12}+\dfrac{2}{12}\)

\(=\dfrac{7}{12}\)

e) \(\dfrac{4}{5}-\dfrac{1}{5}\times\dfrac{7}{2}\)

\(=\dfrac{4}{5}-\dfrac{1\times7}{5\times2}\)

\(=\dfrac{4}{5}-\dfrac{7}{10}\)

\(=\dfrac{8}{10}-\dfrac{7}{10}\)

\(=\dfrac{8-7}{10}\)

\(=\dfrac{1}{10}\)

f) \(\dfrac{16}{9}-\dfrac{4}{15}:\dfrac{2}{5}\)

\(=\dfrac{16}{9}-\dfrac{4}{15}\times\dfrac{5}{2}\)

\(=\dfrac{16}{9}-\dfrac{4\times5}{15\times2}\)

\(=\dfrac{16}{9}-\dfrac{2}{3}\)

\(=\dfrac{16}{9}-\dfrac{6}{9}\)

\(=\dfrac{16-6}{9}\)

\(=\dfrac{10}{9}\)

a: =8/4+3/4=11/4

b: =4/12+18/12-21/12=1/12

c: =4/24+9/24-6/24=7/24

d: =5/12+12/72

=5/12+1/6

=5/12+2/12=7/12

e: =4/5-7/10

=8/10-7/10=1/10

f: =16/9-4/15*5/2

=16/9-20/30

=16/9-2/3

=16/9-6/9=10/9

`@` `\text {Ans}`

`\downarrow`

`a,`

`2 + 3/4`

`= 8/4 + 3/4`

`= 11/4`

`b,`

`1/3 + 3/2 - 7/4`

`= 4/12 + 18/12 - 21/12`

`= 1/12`

`c,`

`1/6 + 3/8 - 1/4`

`= 4/24 + 9/24 - 6/24`

`=7/24`

`d,`

`5/12+3/8  \times 4/9`

`= 5/12 + 27/32`

`= 121/96`

`e,`

`4/5-1/5 \times 7/2`

`= 4/5 - 2/35`

`=26/35`

`f,`

`16/9-4/15 \div 2/5`

`= 16/9 - 2/3`

`= 10/9`

$#KDN040510$