\(=\dfrac{3}{7}\cdot\dfrac{7}{3}\cdot\dfrac{7}{3}\cdot\dfrac{3}{7}\cdot\dfrac{7}{3}=1\cdot1\cdot\dfrac{7}{3}=\dfrac{7}{3}\)

Ta có: \(\dfrac{4}{3\cdot7}+\dfrac{4}{7\cdot11}+\dfrac{4}{11\cdot15}+...+\dfrac{4}{23\cdot27}\)

\(=\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{15}+...+\dfrac{1}{23}-\dfrac{1}{27}\)

\(=\dfrac{1}{3}-\dfrac{1}{27}=\dfrac{8}{27}\)

\(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+...+\frac{4}{100.104}\)

\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+...+\frac{1}{100}-\frac{1}{104}\)

\(=\frac{1}{3}-\frac{1}{104}=\frac{104}{312}-\frac{3}{312}=\frac{101}{312}\)

a/\(\frac{2^3\cdot3^4}{2^2\cdot3^2\cdot5}=\frac{18}{5}\)\(\frac{2^4\cdot5^2\cdot11^2\cdot7}{2^3\cdot5^3\cdot7^2\cdot11}=\frac{2\cdot11}{5\cdot7}=\frac{22}{35}\)

b/\(\frac{121\cdot75\cdot130\cdot169}{39\cdot60\cdot11\cdot198}=\frac{11^2\cdot5^3\cdot13^3\cdot2\cdot3}{2^3\cdot3^4\cdot5\cdot11^2\cdot13}=\frac{5^2\cdot13^2}{2^2\cdot3^3}=\frac{4225}{108}\)

c/\(\frac{1998\cdot1990+3978}{1992\cdot1991-3984}=\frac{2^2\cdot3^3\cdot37\cdot5\cdot199+2\cdot3^2\cdot13\cdot17}{2^3\cdot3\cdot83\cdot11\cdot181-2^4\cdot3\cdot83}=\frac{2\cdot3^2\cdot11\cdot20101}{2^3\cdot3^3\cdot13\cdot17\cdot83}=\frac{11\cdot20101}{2^2\cdot3\cdot13\cdot17\cdot83}\)

19/20x2/100+19/20x2/100

= [19/20+19/20]x2/100

= 38/20x2/100

= 19/500

75/76x102/100-75/76x2/100

= [102/100-2/100]x75/76

= 1x75/76

= 75/76

3x7/10+7/10x5+2x7/10

= [3+5+2]x7/10

= 10x7/10

= 7

giá trị biểu thức 

2/5+2/3x3/4

= 2/5+1/6

= 17/30

1/2x1/3-1/8

= 1/6-1/8

= 1/24

[1/2+1/3]:3/9

= 5/6:3/9

= 5/2

                       nhớ tick cho tớ nhé

rùi đó

\(A=\dfrac{4}{3.7}+\dfrac{4}{7.11}+\dfrac{4}{11.15}+\dfrac{4}{15.19}+\dfrac{4}{19.23}+\dfrac{4}{23.27}\)(Dấu . là dấu nhân)
\(=\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{27}\)
\(=\dfrac{1}{3}-\dfrac{1}{27}\)
\(=\dfrac{9}{27}-\dfrac{1}{27}\)
\(=\dfrac{8}{27}\)

A = 4/3x7 + 4/7x11+ 4/11x15 + 4/15x19 + 4/19 x23 + 4/23 x 27

A = 1/3-1/7+1/7-1/11+1/11-1/15+1/15-1/19+1/19-1/23+1/23 -1/27

A = 1/3 - 1/27

A = 8/27

3 x 7/10 + 7/10  x 5 +2 x 7/10 

=7/10 x (3 + 5 + 2)

= 7/10 x 10

= 70/10=7

hok tốt nha

\(3\times\frac{7}{10}+\frac{7}{10}\times5+2\times\frac{7}{10}\)

\(=\frac{7}{10}\times\left(3+5+2\right)\)

\(=\frac{7}{10}\times10=\frac{7\times10}{10}=7\)

=(3 + 5 + 2) x 7/10

=10 x 7/10

= 7

a) 4 x 5 - 4 x 2 + 4

= 4 x 5 - 4 x 2 + 4 x 1

= 4 x ( 5 - 2 + 1 )

= 4 x 4

= 16

b) 2 x 3 + 9 + 3 x 3

= 2 x 3 + 3 x 3 + 3 x 3

= 3 x ( 2 + 3 + 3 )

= 3 x 8

= 24

c) 2 + 2 x 9

= 2 x 1 + 2 x 9

= 2 x ( 1 + 9 )

= 2 x 10

= 20

a) 4 x 5 - 4 x 2 + 4

= 4 x 5 - 4 x 2 + 4 x 1

= 4 x ( 5 - 2 + 1 )

= 4 x 4

= 16

b) 2 x 3 + 9 + 3 x 3

= 2 x 3 + 3 x 3 + 3 x 3

= 3 x ( 2 + 3 + 3 )

= 3 x 8

= 24

c) 2 + 2 x 9

= 2 x 1 + 2 x 9

= 2 x ( 1 + 9 )

= 2 x 10

= 20

Đáp án đây nhé