=31.22554945

mình chịu

mk cung co bai giong ban , neu ban giai duoc roi thi nhan tin va chi mk nha

3/ 4x7 + 1 / 7 x 8 + 5 / 8  x13 + 2 / 13 x 15 + 9 / 15 x 24

= 1/ 4-1/7+ 1 / 7 - 1/8 + 1/ 8 - 1/ 13 + 1/ 13 - 1/ 15 + 1/ 15 - 1/24

= 1/ 4 - 1/24

=5/ 24

\(78-\left(x-25\right).3\frac{1}{3}=73\)

\(78-\left(x-25\right)\cdot\frac{10}{3}=73\)

\(\left(x-25\right)\cdot\frac{10}{3}=78-73\)

\(\left(x-25\right)\cdot\frac{10}{3}=5\)

\(x-25=5:\frac{10}{3}\)

\(x-25=1,5\)

\(x=25+1,5=26,5\)

19x64+76x34

=(19x4)x16+76x34

=76x(16+34)

=76x50

=3800

a) 19 x 64 + 76 x 34

= 19 x 64 + 19 x 4 x 34

= 19 x ( 64 + 4 x 34 )

= 19 x 200

= 3800

k cho mình rùi mình giải bài b) cho

   136 x 68 + 16 x 272

= 136 x 68 + 16 x  2 x 136

= 136 x 68 + 32 x 136

= 136 x ( 68 + 32 )

= 136 x 100

= 13600    

136x68+16x272

=9248 + 4352

=13600

tk cho mik nha

Tìm x :

2,8 : x - 1,5 = 2,3 : 5,75

=> x - 1,5 = 5,75

     x         = 5,75 + 1,5

     x         = 7,25

Tính nhanh :

\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{13\times14}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{13}-\frac{1}{14}\)

\(=1-\frac{1}{14}+0+...+0\)

\(=\frac{13}{14}\)

1. 2,8 : x - 1,5 = 2,3 : 5,75

    2,8 : x - 1,5 = 0,4

    2,8 : x = 0,4 + 1,5

    2,8 : x = 1,9

            x = 2,8 : 1,9

            x = 1,473

2. \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{13.14}\)

= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{13}-\frac{1}{14}\)

= \(1-\frac{1}{14}\)

= \(\frac{13}{14}\)

\(\frac{3}{4\times7}+\frac{1}{7\times8}+\frac{5}{8\times13}+\frac{2}{13\times15}+\frac{9}{15\times24}\)

=  \(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{24}\)

= \(\frac{1}{4}-\frac{1}{24}\)

=  \(\frac{6}{24}-\frac{1}{24}\)

= \(\frac{5}{24}\)

\(\frac{3}{4.7}+\frac{1}{1.8}+\frac{5}{8.13}+\frac{2}{13.15}+\frac{9}{15.24}\)

Đặt A = ( 3 + 1 + 5 + 2 + 9 ) . \(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{24}\)

      A = 20 . \(\frac{1}{4}-\frac{1}{24}\)

      A = 20 . \(\frac{6}{24}-\frac{1}{24}\)

      A  = 20 . \(\frac{5}{24}\)

      A  = \(\frac{100}{24}\)

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Học tốt

# DanLinh

Bạn Dan Linh ơi dãy số: \(\frac{3}{4\times7}+\frac{1}{7\times8}+\frac{5}{8\times13}+\frac{2}{13\times15}+\frac{9}{15\times24}\)

Không có chung ( 3 + 1 + 5 + 2 + 9 ) mà bạn lại đặt ra là sao vậy

a) 35 x 34 + 35 x 38 + 65 x 75 + 65 x 45

  = 35 x (34+38)  + 65 x (75 + 45)

  = 35 x 72   +    65 x 120

  =  2520 + 7800 = 10320

b)  3 x 25 x 8 + 4 x 37 x 6 + 2 x 38 x 12

 = 3 x ( 25 x 8) + 4 x (37 x 6) + 2 x (38 x 12)

 = 3 x 200 + 4 x 222 + 2 x 456

= 600 + 888 + 912 = 2400

tk nha

35 x 34 + 35 x 38 + 65 x 75 + 65 x 45 

= 35 x ( 34 + 38 ) + 65 x ( 45 + 75 )

= 35 x 72 + 65 x 120

Vì quy tắc thực hiện tính toán phải làm nhân chia trước nên :

= (35 x 34)+(35 x 38)+(65 x 75)+(65 x 45)

= (1190 + 1330) + (4875 + 2925)

= 2520 + 7800

=10320

b) (3 x 25 x 8) +( 4 x 37 x  6) + (2 x 38 x 12)

= 600 + 888 + 912

= 2400

7 - ( 11 + x - 13 ) : 2 ??? 2/3 = 2 

7 - ( 11 + x - 13 ) : 2  2/3 = 2

đề sai à

=31.22554945

\(\frac{3}{4.7}+\frac{1}{7.8}+\frac{5}{8.13}+\frac{2}{13.15}+\frac{9}{15.24}\)

\(=\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{24}\)

\(=\frac{1}{4}-\frac{1}{24}\)

\(=\frac{5}{24}\)

\(\frac{3}{4\cdot7}+\frac{1}{7\cdot8}+\frac{5}{8\cdot13}+\frac{2}{13\cdot15}+\frac{9}{15\cdot24}\)

\(=\frac{7-4}{4\cdot7}+\frac{8-7}{7\cdot8}+\frac{13-8}{8\cdot13}+\frac{15-13}{13\cdot15}+\frac{24-15}{15\cdot24}\)

\(=\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{24}\)

\(=\frac{1}{4}-\frac{1}{24}=\frac{5}{24}\)

Vậy \(\frac{3}{4\cdot7}+\frac{1}{7\cdot8}+\frac{5}{8\cdot13}+\frac{2}{13\cdot15}+\frac{9}{15\cdot24}=\frac{5}{24}\)