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18 tháng 10 2023

\(1+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}\)

\(=\dfrac{5}{4}+\dfrac{1}{8}+\dfrac{1}{16}\)

\(=\dfrac{11}{8}+\dfrac{1}{16}\)

\(=\dfrac{23}{16}\)

______

\(2-\dfrac{1}{8}-\dfrac{1}{12}-\dfrac{1}{16}\)

\(=\dfrac{15}{8}-\dfrac{1}{12}-\dfrac{1}{16}\)

\(=\dfrac{43}{24}-\dfrac{1}{16}\)

\(=\dfrac{83}{48}\)

_________

\(\dfrac{4}{99}\times\dfrac{18}{5}:\dfrac{12}{11}+\dfrac{3}{5}\)

\(=\dfrac{8}{55}:\dfrac{12}{11}+\dfrac{3}{5}\)

\(=\dfrac{8}{55}\times\dfrac{11}{12}+\dfrac{3}{5}\)

\(=\dfrac{2}{15}+\dfrac{3}{5}\)

\(=\dfrac{11}{15}\)

__________

\(\left(1-\dfrac{3}{4}\right)\times\left(1+\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{3}\right)\)

\(=\dfrac{1}{4}\times\dfrac{4}{3}\times\dfrac{2}{3}\)

\(=\dfrac{4\times2}{4\times3\times3}\)

\(=\dfrac{2}{3\times3}\)

\(=\dfrac{2}{9}\)

25 tháng 11 2016

a)\(\frac{1}{5\cdot8}+\frac{1}{8\cdot11}+...+\frac{1}{x\left(x+3\right)}=\frac{101}{1540}\)

\(\Leftrightarrow\frac{1}{3}\left(\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+...+\frac{3}{x\left(x+3\right)}\right)=\frac{101}{1540}\)

\(\Leftrightarrow\frac{1}{3}\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{101}{1540}\)

\(\Leftrightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{303}{1540}\)\(\Leftrightarrow\frac{1}{x+3}=\frac{1}{308}\)

\(\Leftrightarrow x+3=308\Leftrightarrow x=305\)

b ko hiểu đề

6 tháng 8 2020

mù mắt

6 tháng 8 2020

là sao bạn NGUYỄN HỮU CHUNG 

21 tháng 10 2023

a) 1 + 1/4 + 1/8 + 1/16

= 16/16 + 4/16 + 2/16 + 1/16

= 23/16

b) 2 - 1/8 - 1/12 - 1/16

= 96/48 - 6/46 - 4/48 - 3/48

= 83/48

c) 4/99 × 18/5 : 12/11 + 3/5

= 8/55 : 12/11 + 3/5

= 2/15 + 3/5

= 2/15 + 9/15

= 11/15

d) (1 - 3/4) × (1 + 1/3) : (1 - 1/3)

= 1/4 × 4/3 : 2/3

= 1/3 : 2/3

= 2

21 tháng 10 2023

1 + 1/4 + 1/8 + 1/16

= 16 + 4 + 2 + 1 / 16

=23/16

2-1/8-1/12-1/16

= 96 - 6 - 4 - 3 / 48

= 83 / 48

4/99 x 18/5 : 12 /11 + 3/5

= 4/99 x 18/5 x 11/12 + 3/5

= 2/15 + 3/5

= 11/15

(1 - 3/4) x (1+1/3) : (1-1/3) 

= 1/4 x 4/3 : 2/3

= 1/4 x 4/3 x 3/2

= 1/2

31 tháng 7 2023

A = 13/21.2/11 + 13/21.9/11 + 8/21
= (13/21) + (13/21) + (8/21)
= (13 + 13 + 8)/21
= 34/21

B = (1 - 1/5)(1 - 2/5)(1 - 3/5)...(1 - 9/5)
= (4/5)(3/5)(2/5)(1/5)(0/5)(-1/5)(-2/5)(-3/5)(-4/5)
= 0

C = (1 - 1/2)(1 - 1/3)(1 - 1/4)...(1 - 1/50)
= (1/2)(2/3)(3/4)(4/5)...(49/50)
= 1/50

D = (2^2/1.3) * (3^2/2.4) * (4^2/3.5) * (5^2/4.6) * (6^2/5.7)
= (4/3) * (9/8) * (16/15) * (25/23) * (36/35)
= 0.979