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18 tháng 9 2018

ta có B = \(\dfrac{45}{12.21}+\dfrac{45}{21.30}-\left(\dfrac{40}{24.34}+...+\dfrac{40}{54.64}\right)\)

\(=5\left(\dfrac{9}{12.21}+\dfrac{9}{21.30}\right)-4\left(\dfrac{10}{24.34}+...+\dfrac{10}{54.64}\right)\)

\(=5\left(\dfrac{1}{12}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{30}\right)-4\left(\dfrac{1}{24}-\dfrac{1}{34}+\dfrac{1}{34}-\dfrac{1}{44}+...+\dfrac{1}{54}-\dfrac{1}{64}\right)\)

\(=5\left(\dfrac{1}{12}-\dfrac{1}{30}\right)-4\left(\dfrac{1}{24}-\dfrac{1}{64}\right)\)

\(=5.\dfrac{1}{20}-4.\dfrac{5}{192}\)

\(=5.\dfrac{1}{20}-\dfrac{4}{192}.5\)

\(=5\left(\dfrac{1}{20}-\dfrac{4}{192}\right)=5.\dfrac{7}{240}=\dfrac{7}{48}\)

18 tháng 9 2018

B=5(1/12−1/21+1/21−1/30)−5(1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64)

B=5(1/12−1/21+1/21−1/30+1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64 )

B=5(1/12−1/64)=5.13/192=65/192

18 tháng 9 2018

Đáp án :\(\frac{65}{192}\)

a: \(\dfrac{-13}{40}< \dfrac{-12}{40}\)

\(\dfrac{-5}{6}>\dfrac{-91}{104}\)

17 tháng 7 2023

Sao bn giống BT mình thế ?:)

16 tháng 2 2022

\(\dfrac{20}{45};\dfrac{32}{72}\)

16 tháng 2 2022

\(\dfrac{20}{45},\dfrac{32}{72},\)

18 tháng 11 2018

\(A=\dfrac{1}{8.14}+\dfrac{1}{14.20}+\dfrac{1}{20.26}+...+\dfrac{1}{50.56}\)

\(A=\dfrac{1}{6}.\left(\dfrac{6}{8.14}+\dfrac{6}{14.20}+\dfrac{6}{20.26}+...+\dfrac{6}{50.56}\right)\)

\(A=\dfrac{1}{6}.\left(\dfrac{1}{8}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{20}+\dfrac{1}{20}-\dfrac{1}{26}+...+\dfrac{1}{50}-\dfrac{1}{56}\right)\)

\(A=\dfrac{1}{6}.\left(\dfrac{1}{8}-\dfrac{1}{56}\right)\)

\(A=\dfrac{1}{6}.\left(\dfrac{7}{56}-\dfrac{1}{56}\right)\)

\(A=\dfrac{1}{6}.\dfrac{6}{56}\)

\(A=\dfrac{1}{1}.\dfrac{1}{56}\)

\(A=\dfrac{1}{56}\)

\(B=\dfrac{45}{12.21}+\dfrac{45}{21.30}-\dfrac{40}{24.34}-\dfrac{40}{34.44}-\dfrac{40}{44.54}-\dfrac{40}{54.64}\)

\(B=5\left(\dfrac{9}{12.21}+\dfrac{9}{21.30}\right)-4\left(\dfrac{10}{24.34}+\dfrac{10}{34.44}+\dfrac{10}{44.54}+\dfrac{10}{54.64}\right)\)

\(B=5\left(\dfrac{1}{12}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{30}\right)-4\left(\dfrac{1}{24}-\dfrac{1}{34}+\dfrac{1}{34}-\dfrac{1}{44}+\dfrac{1}{44}-\dfrac{1}{54}+\dfrac{1}{54}-\dfrac{1}{64}\right)\)\(B=5\left(\dfrac{5}{60}-\dfrac{2}{60}\right)-4\left(\dfrac{1}{24}-\dfrac{1}{64}\right)\)

\(B=5.\dfrac{3}{60}-\left(\dfrac{4}{24}-\dfrac{4}{64}\right)\)

\(B=5.\dfrac{1}{20}-\left(\dfrac{1}{6}-\dfrac{1}{16}\right)\)

\(B=\dfrac{5}{20}-\left(\dfrac{8}{48}-\dfrac{3}{48}\right)\)

\(B=\dfrac{1}{4}-\dfrac{5}{48}\)

\(B=\dfrac{12}{48}-\dfrac{5}{48}\)

\(B=\dfrac{7}{48}\)

\(\dfrac{A}{B}=\dfrac{1}{56}:\dfrac{7}{48}\)

\(\dfrac{A}{B}=\dfrac{1}{56}.\dfrac{48}{7}\)

\(\dfrac{A}{B}=\dfrac{1}{7}.\dfrac{6}{7}\)

\(\dfrac{A}{B}=\dfrac{6}{49}=\dfrac{48}{392}< \dfrac{49}{392}=\dfrac{1}{8}\)

\(\dfrac{A}{B}< \dfrac{1}{8}\)

Vậy \(\dfrac{A}{B}< \dfrac{1}{8}\)

29 tháng 10 2023

a: \(\dfrac{8}{18}+\dfrac{5}{3}=\dfrac{4}{9}+\dfrac{5}{3}=\dfrac{4}{9}+\dfrac{15}{9}=\dfrac{4+15}{9}=\dfrac{19}{9}\)

b: \(\dfrac{8}{24}+\dfrac{4}{48}=\dfrac{1}{3}+\dfrac{1}{12}=\dfrac{4}{12}+\dfrac{1}{12}=\dfrac{4+1}{12}=\dfrac{5}{12}\)

c: \(\dfrac{20}{15}-\dfrac{4}{45}=\dfrac{4}{3}-\dfrac{4}{45}=\dfrac{60}{45}-\dfrac{4}{45}=\dfrac{60-4}{45}=\dfrac{56}{45}\)

d: \(\dfrac{40}{32}-\dfrac{1}{2}=\dfrac{5}{4}-\dfrac{1}{2}=\dfrac{5-2}{4}=\dfrac{3}{4}\)

26 tháng 12 2022

ai có thể chỉ giúp tôi được ko vì tôi cần rất gấp

26 tháng 12 2022

\(a,\dfrac{-5}{13}+\dfrac{8}{13}=\dfrac{3}{13}\\ b,\dfrac{5}{31}+\dfrac{-22}{31}=\dfrac{-17}{31}\\ c,\dfrac{-13}{43}+\dfrac{-40}{43}=\dfrac{-53}{43}\\ d,\dfrac{-3}{29}-\dfrac{16}{58}=\dfrac{-11}{29}\\ e,\dfrac{8}{40}-\dfrac{-36}{45}=1\\ f,\dfrac{-8}{18}-\dfrac{-15}{27}=\dfrac{1}{9}\\ g,\left(-2\right)+\dfrac{-5}{8}=\dfrac{-21}{8}\)

25 tháng 2 2019

\(\dfrac{11}{24}\)banh

24 tháng 8 2023

a) \(\dfrac{56}{42}=\dfrac{28}{21}=\dfrac{4}{3}\)

\(\dfrac{16}{24}=\dfrac{2}{3}=\dfrac{8}{12}=\dfrac{40}{60}\)

b) \(\dfrac{40}{25}=\dfrac{8}{5}\)

\(\dfrac{63}{81}=\dfrac{7}{9}\)

\(\dfrac{36}{60}=\dfrac{3}{5}\)