tìm x:
\(\left(1-\dfrac{1}{2}\right)\cdot\left(1-\dfrac{1}{3}\right)\cdot\left(1-\dfrac{1}{4}\right)\cdot...\cdot\left(1-\dfrac{1}{10}\right)=\dfrac{x}{2010}\)
Tính :
a) \(\dfrac{2}{3}+\dfrac{1}{5}.\dfrac{10}{7}\)
b) \(\dfrac{7}{12}-\dfrac{27}{7}.\dfrac{1}{18}\)
c) \(\left(\dfrac{23}{41}-\dfrac{15}{82}\right).\dfrac{41}{25}\)
d) \(\left(\dfrac{4}{5}+\dfrac{1}{2}\right).\left(\dfrac{3}{13}-\dfrac{8}{13}\right)\)
Tính một cách hợp lý:
a\(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right)...\left(\dfrac{1}{100}-1\right)\)) \(x:\dfrac{99}{100}:\dfrac{98}{99}:...:\dfrac{2}{3}:\dfrac{1}{2}\)
b) \(\dfrac{5-\dfrac{5}{3}+\dfrac{5}{9}-\dfrac{5}{27}}{8-\dfrac{8}{3}+\dfrac{8}{9}-\dfrac{8}{27}}:\dfrac{15-\dfrac{15}{11}+\dfrac{15}{121}}{16-\dfrac{16}{11}+\dfrac{16}{121}}\)
c) \(\dfrac{\dfrac{1}{9}-\dfrac{5}{6}-4}{\dfrac{7}{12}-\dfrac{1}{36}-10}\)
d) \(\left(\dfrac{1}{2}+1\right)\left(\dfrac{1}{3}+1\right)...\left(\dfrac{1}{99}+1\right)\)
e)
Câu 1 :\(\dfrac{-5}{7}.\dfrac{7}{-45}\);\(\dfrac{-3}{10}.\left(-30\right)\);\(-12.\dfrac{-2}{36}\)
Câu 2: \(\dfrac{3}{4}+\dfrac{1}{8}.\dfrac{-16}{5};\dfrac{7}{15}-\dfrac{18}{21}.\dfrac{7}{9}\)
Câu 3: \(\left(\dfrac{-5}{9}+\dfrac{3}{5}\right).\dfrac{3}{10};\left(\dfrac{3}{9}-\dfrac{2}{5}\right).\dfrac{-3}{10}\)
Câu 4: \(\left(\dfrac{3}{7}+\dfrac{1}{3}\right).\left(\dfrac{1}{8}-\dfrac{1}{2}\right);\left(\dfrac{-9}{12}-\dfrac{16}{30}\right).\left(\dfrac{-18}{22}-\dfrac{6}{11}\right)\)
Càn gấp
a) \(\dfrac{-21}{15}\).\(\dfrac{-10}{14}\) b)\(\left(-\dfrac{2}{3}\right)^2\) c)\(\dfrac{-3}{4}\).\(\dfrac{-4}{5}\).\(\dfrac{16}{9}\) d)\(\dfrac{-8}{3}\).\(\dfrac{5}{6}\) e)\(\dfrac{16}{30}\).\(\dfrac{5}{12}\) f) \(\dfrac{13}{30}\).\(\dfrac{-1}{5}\) g)\(\dfrac{2}{21}\).\(\dfrac{3}{28}\) h)\(\left(\dfrac{-3}{4}\right)^3\)
Tìm x biết
a)\(\dfrac{11}{12}\).x + \(\dfrac{3}{4}\)= -\(\dfrac{1}{6}\)
b)3-\(\left(\dfrac{1}{6}-x\right)\).\(\dfrac{2}{3}\)=\(\dfrac{2}{3}\)
C=\(\dfrac{2}{15}+\dfrac{2}{35}+\dfrac{2}{63}+...+\dfrac{2}{399}\)
E=\(\dfrac{6}{1.3.7}+\dfrac{6}{6.7.9}+...+\dfrac{6}{13.15.19}\)
F=\(\dfrac{92-\dfrac{1}{9}-\dfrac{2}{10}-\dfrac{3}{11}-...-\dfrac{92}{100}}{\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}}\)
G=\(10-\dfrac{1}{72}-\dfrac{1}{56}-\dfrac{1}{42}-...-\dfrac{1}{6}-\dfrac{1}{2}\)
Tính :
a) \(\dfrac{-8}{13}.26\)
b) \(\left(\dfrac{-2}{7}\right)^2\)
c) \(\left(2-\dfrac{1}{2}\right).\left(\dfrac{-3}{4}+\dfrac{1}{2}\right)\)
Tính hợp lí:
\(-\dfrac{2}{7}.(\dfrac{5}{13}-\dfrac{9}{15})_{ }-\dfrac{2}{7}.\dfrac{8}{13}\)
