Tính nhanh:
\(\dfrac{17}{13}:\dfrac{51}{26}=\dfrac{17}{13}x\dfrac{26}{51}=\dfrac{17x13x2}{13x17x3}=\dfrac{2}{3}\)
\(\dfrac{33}{38}:\dfrac{11}{19}\)=?
BT2: Tính nhanh:
9)\(\dfrac{47}{51}\left(\dfrac{17}{94}-\dfrac{53}{91}\right)-\dfrac{53}{91}\left(\dfrac{91}{53}-\dfrac{47}{51}\right)\)
10)\(\dfrac{13}{19}\left(\dfrac{19}{26}-\dfrac{71}{43}\right)+\dfrac{71}{43}\left(\dfrac{13}{19}-\dfrac{86}{71}\right)\)
9: \(=\dfrac{47}{51}\cdot\dfrac{17}{94}-\dfrac{47}{51}\cdot\dfrac{53}{91}-\dfrac{53}{91}\cdot\dfrac{91}{53}+\dfrac{53}{91}\cdot\dfrac{47}{51}\)
\(=\dfrac{1}{6}-1=-\dfrac{5}{6}\)
10: \(=\dfrac{13}{19}\cdot\dfrac{19}{26}-\dfrac{13}{19}\cdot\dfrac{71}{43}+\dfrac{71}{43}\cdot\dfrac{13}{19}-\dfrac{71}{43}\cdot\dfrac{86}{71}\)
\(=\dfrac{1}{2}-2=-\dfrac{3}{2}\)
bài 1 tính :
\(\dfrac{-8}{9}\) . \(\dfrac{12}{19}\) . \(\dfrac{9}{-4}\) . \(\dfrac{19}{24}\) \(\dfrac{-5}{16}\) . \(\dfrac{17}{15}\) : \(\dfrac{-17}{8}\)
\(\dfrac{4}{13}\) . \(\dfrac{2}{7}\) + \(\dfrac{-3}{26}\) + \(\dfrac{4}{13}\) . \(\dfrac{5}{7}\) \(\dfrac{6}{11}\) . \(\dfrac{3}{4}\) + \(\dfrac{-12}{60}\) +\(\dfrac{-3}{4}\) .\(\dfrac{-5}{11}\)
giúp mk vs mn ơi , mai cô giáo ktra mk r
a: \(=\dfrac{8}{9}\cdot\dfrac{9}{4}\cdot\dfrac{12}{19}\cdot\dfrac{19}{24}=\dfrac{1}{2}\cdot2=1\)
b: \(=\dfrac{5}{16}\cdot\dfrac{17}{15}\cdot\dfrac{8}{17}=\dfrac{5}{16}\cdot\dfrac{8}{15}=\dfrac{40}{240}=\dfrac{1}{6}\)
c: \(=\dfrac{4}{13}\left(\dfrac{2}{7}+\dfrac{5}{7}\right)-\dfrac{3}{26}=\dfrac{4}{13}-\dfrac{3}{26}=\dfrac{5}{26}\)
c: \(=\dfrac{3}{4}\left(\dfrac{6}{11}+\dfrac{5}{11}\right)-\dfrac{1}{5}=\dfrac{3}{4}-\dfrac{1}{5}=\dfrac{11}{20}\)
>; <; = ?
a) \(\dfrac{21}{23}\) ? \(\dfrac{19}{23}\) \(\dfrac{8}{5}\) ? \(\dfrac{49}{30}\) \(\dfrac{20}{36}\) ? \(\dfrac{5}{9}\)
b) \(\dfrac{11}{15}\) ? \(\dfrac{11}{17}\) \(\dfrac{26}{13}\) ? 2 3 ? \(\dfrac{16}{5}\)
c) \(\dfrac{8}{9}\) ? 1 1 ? \(\dfrac{31}{27}\) \(\dfrac{8}{9}\) ? \(\dfrac{31}{27}\)
a) \(\dfrac{21}{23}>\dfrac{19}{23}\)
\(\dfrac{8}{5}=\dfrac{49}{30}\)
\(\dfrac{23}{36}>\dfrac{5}{9}\)
b) \(\dfrac{11}{15}>\dfrac{11}{17}\)
\(\dfrac{26}{13}=2\)
\(3< \dfrac{16}{5}\)
c) \(\dfrac{8}{9}< 1\)
\(1< \dfrac{31}{27}\)
\(\dfrac{8}{9}< \dfrac{31}{27}\)
\(Chobaitoansau:\)
\(M=\dfrac{75-\dfrac{6}{13}+\dfrac{3}{17}-\dfrac{3}{19}}{257-\dfrac{22}{13}+\dfrac{11}{17}-\dfrac{11}{19}}\)
\(2N=\dfrac{1,1+0,19-1,32}{2,06+0,54}-\left(\dfrac{1}{2}+\dfrac{1}{3}\right):2\)
\(P=\left(5\dfrac{7}{8}-2\dfrac{1}{4}-0,5\right):2\dfrac{23}{26}\)
a, Tính M, P
b, Tìm x∈ Z, biết N < x < P
Tính nhanh :
\(\dfrac{13}{17}+\dfrac{2}{13}+\dfrac{4}{17}+.......+\dfrac{11}{13}\)
( \(\dfrac{13}{17}\) + \(\dfrac{4}{17}\) ) + (\(\dfrac{2}{13}\) + \(\dfrac{11}{13}\) ) = \(\dfrac{17}{17}\) + \(\dfrac{13}{13}\) = \(1\) + \(1\) = \(2\).
Tìm số nguyên x, biết: ( \(\dfrac{31}{20}-\dfrac{26}{45}\) ) . \(\dfrac{-36}{35}< x< \left(\dfrac{51}{56}+\dfrac{8}{21}+\dfrac{1}{3}\right).\dfrac{8}{13}\)
=\(\dfrac{35}{36}.\dfrac{-36}{35}< x< \dfrac{13}{8}.\dfrac{8}{13}\)
= -1 < x < 1
vậy x = 0
-(\(\dfrac{3}{17}\)+\(\dfrac{2}{13}\))-(\(\dfrac{-20}{17}\)+\(\dfrac{11}{13}\)) Tính nhanh từng bước ra nha
\(=\dfrac{-3}{17}-\dfrac{2}{13}+\dfrac{20}{17}-\dfrac{11}{13}\)
=1-1
=0
\(-\left(\dfrac{3}{17}+\dfrac{2}{13}\right)-\left(\dfrac{-20}{17}+\dfrac{11}{13}\right)\)
\(=-\dfrac{3}{17}-\dfrac{2}{13}-\dfrac{20}{17}-\dfrac{11}{13}\)
\(=-\left(\dfrac{3}{17}+\dfrac{20}{17}\right)-\left(\dfrac{2}{13}+\dfrac{11}{13}\right)\)
\(=-\dfrac{23}{17}-1\)
\(=-\dfrac{40}{17}\)
\(-\left(\dfrac{3}{17}+\dfrac{2}{13}\right)-\left(\dfrac{-20}{17}+\dfrac{11}{13}\right)\)
⇔ \(\dfrac{-3}{17}-\dfrac{2}{13}+\dfrac{20}{17}-\dfrac{11}{13}\)
⇔ \(\left(\dfrac{-3}{17}+\dfrac{20}{17}\right)+\left(\dfrac{-2}{13}-\dfrac{11}{13}\right)\)
⇔ \(1+\left(-1\right)\)
⇔ \(0\)
A = \(\dfrac{28}{25}\) + \(\dfrac{9}{10}\) - \(\dfrac{11}{15}\) + \(\dfrac{13}{21}\) - \(\dfrac{15}{28}\) + \(\dfrac{17}{26}\) - ... + \(\dfrac{197}{4851}\) - \(\dfrac{199}{4950}\)
8) \(\dfrac{17}{-26}.\left(\dfrac{1}{6}-\dfrac{5}{3}\right):\dfrac{17}{13}-\dfrac{20}{3}.\left(\dfrac{2}{5}-\dfrac{1}{4}\right)+\dfrac{2}{3}.\left(\dfrac{6}{5}-\dfrac{9}{2}\right)\)
\(\dfrac{17}{-26}\cdot\left(\dfrac{1}{6}-\dfrac{5}{3}\right):\dfrac{17}{13}-\dfrac{20}{3}\cdot\left(\dfrac{2}{5}-\dfrac{1}{4}\right)+\dfrac{2}{3}\left(\dfrac{6}{5}-\dfrac{9}{2}\right)\)
\(=\dfrac{-17}{26}\cdot\dfrac{13}{17}\cdot\dfrac{1-10}{6}-\dfrac{20}{3}\cdot\dfrac{8-5}{20}+\dfrac{2}{3}\cdot\dfrac{12-45}{10}\)
\(=\dfrac{-1}{2}\cdot\dfrac{-9}{6}-\dfrac{20}{3}\cdot\dfrac{3}{20}+\dfrac{2}{3}\cdot\dfrac{-33}{10}\)
\(=\dfrac{3}{4}-1-\dfrac{66}{30}=\dfrac{-1}{4}-\dfrac{11}{5}=\dfrac{-5-44}{20}=-\dfrac{49}{20}\)