Bài 8 :
1)
\(\left(\dfrac{9}{25}-2,18\right):\left(3\dfrac{4}{5}+0,2\right)\)
\(=\left(\dfrac{9}{25}-\dfrac{109}{50}\right):\left(\dfrac{19}{5}+\dfrac{1}{5}\right)\)
\(=\left(\dfrac{18}{50}-\dfrac{109}{50}\right):4\)
\(=\dfrac{-91}{50}:4\)
\(=\dfrac{-91}{200}\)
2)
\(\dfrac{5}{18}-1,456:\dfrac{7}{25}+4,5.\dfrac{4}{5}\)
\(=\dfrac{5}{18}-\dfrac{182}{125}:\dfrac{7}{25}+\dfrac{9}{2}.\dfrac{4}{5}\)
\(=\dfrac{5}{18}-\dfrac{182}{125}.\dfrac{25}{7}+\dfrac{9}{2}.\dfrac{4}{5}\)
\(=\dfrac{5}{18}-\dfrac{26}{5}+\dfrac{18}{5}\)
\(=\dfrac{25}{90}-\dfrac{468}{90}+\dfrac{18}{5}\)
\(=\dfrac{-443}{90}+\dfrac{18}{5}\)
\(=\dfrac{-443}{90}+\dfrac{324}{90}\)
\(=\dfrac{-119}{90}\)
3)
\(1\dfrac{4}{23}+\dfrac{5}{21}-\dfrac{4}{23}+0,5+\dfrac{16}{21}\)
\(=\dfrac{27}{23}+\dfrac{5}{21}-\dfrac{4}{23}+\dfrac{1}{2}+\dfrac{16}{21}\)
\(=\left(\dfrac{27}{23}-\dfrac{4}{23}\right)+\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+\dfrac{1}{2}\)
\(=1+1+\dfrac{1}{2}\)
\(=2+\dfrac{1}{2}\)
\(=\dfrac{5}{2}\)
4)
\(\dfrac{3}{7}.19\dfrac{1}{3}-\dfrac{3}{7}.33\dfrac{1}{3}\)
\(=\dfrac{3}{7}.\dfrac{58}{3}-\dfrac{3}{7}.\dfrac{100}{3}\)
\(=\dfrac{3}{7}.\left(\dfrac{58}{3}-\dfrac{100}{3}\right)\)
\(=\dfrac{3}{7}.\left(-14\right)\)
\(=-6\)
5)
\(9.\left(-\dfrac{1}{3}\right)^3+\dfrac{1}{3}\)
\(=9.\dfrac{-1}{27}+\dfrac{1}{3}\)
\(=\dfrac{-1}{3}+\dfrac{1}{3}\)
\(=0\)
6)
\(15\dfrac{1}{4}:\left(-\dfrac{5}{7}\right)-25\dfrac{1}{4}:\left(-\dfrac{5}{7}\right)\)
\(=\dfrac{61}{4}:\left(-\dfrac{5}{7}\right)-\dfrac{101}{4}:\left(-\dfrac{5}{7}\right)\)
\(=\dfrac{61}{4}.\dfrac{-7}{5}-\dfrac{101}{4}.\dfrac{-7}{5}\)
\(=\dfrac{-7}{5}.\left(\dfrac{61}{4}-\dfrac{101}{4}\right)\)
\(=\dfrac{-7}{5}.\left(-10\right)\)
\(=14\)
\(#Bingchilling-Linh\)
