\(\frac{13}{21}\)+\(\frac{15}{13}\)+\(\frac{14}{5}\)

=\(\frac{845}{1365}\)+\(\frac{1575}{1365}\)+\(\frac{3822}{1365}\)

=\(\frac{6242}{1365}\)

=(4x0.25)x(2x0.5)

=1x1=1

ủa ko biết nữa ko biết nữa ko biết đáp án ở đâu

a) ( 12 + 21 - 23 ) - ( 23 - 21 + 10 )

  = 12 + 21 - 23 - 23 - 21 + 10

  = ( 12 + 10 ) - ( 21 - 21 ) - ( 23 - 23 )

  =        22      -        0        -        0

  =                          22

b) ( 55 + 45 + 15 ) - ( 15 - 55 + 45 )

  = 55 + 45 + 15 - 15 - 55 + 45

  = ( 55 + 45 ) + ( 55 + 45 ) + ( 15 - 15)

  =       100      +      100      +      0

  =                          200

\(a)\)\(-\left(12+21-23\right)-\left(23-21+10\right)\)

 \(=-12-21+23-23+21-10\)

 \(=\left(-21+21\right)+23-23-12-10\)

 \(=0+0-12-10\)

 \(=-22\)

\(b)\)\(\left(55+45+15\right)-\left(15-55+45\right)\)

  \(=55+45+15-15+55-45\)

  \(=\left(15-15\right)+\left(45-45\right)+55+55\)

  \(=0+0+55+55\)

  \(=110\)

1. Tính giá trị biểu thức:

a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145

b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7

c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11

1. Tính giá trị biểu thức:

a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21

b) (5/17 x 21/32 x 47/24 x 0)
= 0

c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7

1. Tìm x:

a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x

b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15

c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2

1. Tìm x:

a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36

câu,b,không,đủ,thông,tin,nhan,bạn.

=15/7*14/25*10/3

= 210/175*10/3

= 2100/525

Chi se giup em

kết quả bằng 4

\(A=\frac{2}{10}+\frac{2}{15}+\frac{2}{21}+...+\frac{2}{120}\)

\(A=\frac{4}{20}+\frac{4}{30}+\frac{4}{42}+...+\frac{4}{240}\)

\(A=\frac{4}{4.5}+\frac{4}{5.6}+\frac{4}{6.7}+...+\frac{4}{15.16}\)

\(A=4.\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{15}-\frac{1}{16}\right)\)

\(A=4.\left(\frac{1}{4}-\frac{1}{16}\right)\)

\(A=4.\left(\frac{4}{16}-\frac{1}{16}\right)\)

\(A=4.\frac{3}{16}=\frac{3}{4}\)

k nha

không hiểu

\(\frac{1}{2}\) E= \(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\)

\(\frac{1}{2}\) E = \(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{8.9}\)

\(\frac{1}{2}E\) = \(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{8}-\frac{1}{9}\)

\(\frac{1}{2}E\) = \(\frac{1}{2}-\frac{1}{9}\)

\(\frac{1}{2}E\) =\(\frac{7}{18}\)

=> E = \(\frac{7}{9}\)

E=\(\frac{1}{3}+\frac{1}{6}+....+\frac{1}{28}+\frac{1}{36}\)

\(\frac{1}{2}E=\frac{1}{6}+\frac{1}{12}+...+\frac{1}{56}+\frac{1}{72}\)

\(\frac{1}{2}E=\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{7.8}+\frac{1}{8.9}\)

\(\frac{1}{2}E=\frac{3-2}{2.3}+\frac{4-3}{3.4}+...\frac{8-7}{7.8}+\frac{9-8}{8.9}\)

\(\frac{1}{2}E=\frac{3}{2.3}-\frac{2}{2.3}+\frac{4}{3.4}-\frac{3}{3.4}+...+\frac{8}{7.8}-\frac{7}{7.8}+\frac{9}{8.9}-\frac{8}{8.9}\)

\(\frac{1}{2}E=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\)

\(\frac{1}{2}E=\frac{1}{2}-\frac{1}{9}=\frac{7}{18}\)

E=\(\frac{7}{18}:\frac{1}{2}=\frac{7}{9}\)