Giải:
\(7,5x:\left(9-6\dfrac{13}{21}\right)=2\dfrac{13}{25}\)
\(\Leftrightarrow7,5x:\left(9-\dfrac{139}{21}\right)=\dfrac{43}{25}\)
\(\Leftrightarrow7,5x:\dfrac{50}{21}=\dfrac{43}{25}\)
\(\Leftrightarrow7,5x=\dfrac{43}{25}.\dfrac{50}{21}\)
\(\Leftrightarrow7,5x=\dfrac{86}{21}\)
\(\Leftrightarrow x=\dfrac{86}{21}:7,5\)
\(\Leftrightarrow x=\dfrac{172}{315}\)
Vậy ...
\(\dfrac{6}{13}\) x \(\dfrac{8}{7}\) + \(\dfrac{6}{13}\) x \(\dfrac{9}{7}\) - \(\dfrac{3}{13}\) x \(\dfrac{6}{7}\)
Help me please
\(\left(\dfrac{2}{3}+\dfrac{2}{13}+\dfrac{2}{11}+\dfrac{2}{6}\right)\) \(\left(\dfrac{5}{4}+\dfrac{5}{7}+\dfrac{5}{6}+\dfrac{5}{11}\right)\)
___________________ X ___________________
\(\left(\dfrac{4}{3}+\dfrac{4}{13}+\dfrac{4}{11}+\dfrac{4}{6}\right)\) \(\left(\dfrac{9}{4}+\dfrac{9}{7}+\dfrac{9}{6}\dfrac{9}{11}\right)\)
Tính :
\(\dfrac{25^5+25^7+25^9}{5^{11}+5^{13}+5^{15}+5^{17}+5^{19}+5^{21}}\)
Tìm x biết: \(\dfrac{13}{14}+\dfrac{13}{35}+\dfrac{13}{65}+\dfrac{13}{104}+...+\dfrac{13}{1274}-x+2\dfrac{1}{5}=0\)
Tìm x, biết:
a) \(\dfrac{3}{4.7}+\dfrac{3}{7.10}+....+\dfrac{3}{x\left(x+3\right)}=\dfrac{9}{38}\)
b) \(\dfrac{1}{21}+\dfrac{1}{28}+\dfrac{1}{36}+...+\dfrac{2}{x\left(x+1\right)}=\dfrac{2}{9}\)
a,\(\dfrac{-5}{9}\)+\(\dfrac{5}{9}\):(1\(\dfrac{2}{3}\)-2\(\dfrac{1}{12}\))
b,\(\dfrac{-7}{25}\).\(\dfrac{11}{13}\)+\(\dfrac{-7}{25}\).\(\dfrac{2}{13}\)-\(\dfrac{18}{25}\)
c,(\(\dfrac{5}{7}\).0,6-5:3\(\dfrac{1}{2}\)).(40%-1,4).\(\left(-2\right)^3\)
Tính nhanh:
\(A=\dfrac{5}{13}=\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
\(Tìm\) \(x\)∈\(Z\)\(,\) \(biết\)\(:\)
\(a\)) \(\left(x-20\right)+\left(x-19\right)+\left(x-18\right)+...+99+100=100\)
\(b\)) \(213-x.\left(\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2020}}\right):\left(1-\dfrac{1}{2^{2020}}\right)=13\)
1. tính
a. \(\dfrac{3}{5}\)-\(\dfrac{2}{3}\)+\(\dfrac{16}{15}\)
b. (\(\dfrac{5}{6}\)-\(\dfrac{4}{5}\)):\(\dfrac{7}{30}\)-\(\dfrac{6}{7}\)
c. \(\dfrac{4}{11}\).\(\dfrac{-2}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{-8}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{1}{9}\)
d.\(\dfrac{-13}{10}\)-\(\dfrac{15}{16}\):\(\dfrac{-3}{4}\)+\(\dfrac{21}{25}\).\(\dfrac{-15}{28}\)
