Bài 3 :
a)
\(\left(\dfrac{2}{3}\right)^3-\left(\dfrac{3}{4}\right)^2.\left(-1\right)^5\)
\(=\dfrac{8}{27}-\dfrac{9}{16}.\left(-1\right)\)
\(=\dfrac{8}{27}-\dfrac{-9}{16}\)
\(=\dfrac{128}{432}-\dfrac{-243}{432}\)
\(=\dfrac{371}{432}\)
b)
\(12:\left(\dfrac{3}{4}-\dfrac{5}{6}\right)^2\)
\(=12:\left(\dfrac{18}{24}-\dfrac{20}{24}\right)^2\)
\(=12:\left(\dfrac{-1}{12}\right)^2\)
\(=12:\dfrac{1}{144}\)
\(=12.\dfrac{144}{1}\)
\(=1728\)
c)
\(\dfrac{7}{22}:\dfrac{3}{11}+\dfrac{7}{22}:\dfrac{4}{11}\)
\(=\dfrac{7}{22}.\dfrac{11}{3}+\dfrac{7}{22}.\dfrac{11}{4}\)
\(=\dfrac{7}{22}.\left(\dfrac{11}{3}+\dfrac{11}{4}\right)\)
\(=\dfrac{7}{22}.\left(\dfrac{44}{12}+\dfrac{33}{12}\right)\)
\(=\dfrac{7}{22}.\dfrac{77}{12}\)
\(=\dfrac{49}{24}\)
d)
\(\dfrac{12}{35}.\left(\dfrac{7}{4}+\dfrac{13}{4}\right)-\dfrac{1}{3}\)
\(=\dfrac{12}{35}.5-\dfrac{1}{3}\)
\(=\dfrac{12}{7}-\dfrac{1}{3}\)
\(=\dfrac{36}{21}-\dfrac{7}{21}\)
\(=\dfrac{29}{21}\)
Bài 4 :
a)
\(\dfrac{3}{7}+\left(-\dfrac{5}{2}\right)+\left(-\dfrac{3}{5}\right)\)
\(=\dfrac{6}{14}+\dfrac{-35}{14}+\dfrac{-3}{5}\)
\(=\dfrac{-29}{14}+\dfrac{-3}{5}\)
\(=\dfrac{-145}{70}+\dfrac{-42}{70}\)
\(=\dfrac{-187}{70}\)
b)
\(\dfrac{-8}{18}-\dfrac{15}{27}\)
\(=\dfrac{-216}{486}-\dfrac{270}{486}\)
\(=-1\)
c)
\(\dfrac{4}{5}-\left(-\dfrac{2}{7}\right)-\dfrac{7}{10}\)
\(=\dfrac{4}{5}+\dfrac{2}{7}-\dfrac{7}{10}\)
\(=\dfrac{28}{35}+\dfrac{10}{35}-\dfrac{7}{10}\)
\(=\dfrac{38}{35}-\dfrac{7}{10}\)
\(=\dfrac{380}{350}-\dfrac{245}{350}\)
\(=\dfrac{27}{70}\)
d)
\(3,5-\left(-\dfrac{2}{7}\right)\)
\(=\dfrac{7}{2}-\left(-\dfrac{2}{7}\right)\)
\(=\dfrac{7}{2}+\dfrac{2}{7}\)
\(=\dfrac{49}{14}+\dfrac{4}{14}\)
\(=\dfrac{53}{14}\)
Bài 4:
a: \(=\dfrac{3}{7}-\dfrac{5}{2}-\dfrac{3}{5}=\dfrac{30-5\cdot35-3\cdot14}{70}=\dfrac{-187}{70}\)
b: \(=\dfrac{-4}{9}-\dfrac{5}{9}=-1\)
c: \(=\dfrac{4}{5}+\dfrac{2}{7}-\dfrac{7}{10}=\dfrac{56+20-49}{70}=\dfrac{27}{70}\)
d: =7/2+2/7
=49/14+4/14
=53/14
