\(\dfrac{7}{15}\),\(\dfrac{-3}{7}\),\(\dfrac{3}{4}\)
giúp mk với
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a. \(\dfrac{-3}{12}+\dfrac{1}{-4}=\dfrac{-3}{12}+\dfrac{-3}{12}=\dfrac{-3-3}{12}=\dfrac{-6}{12}=\dfrac{-1}{2}\)
b. \(\dfrac{5}{12}+\dfrac{-3}{28}=\dfrac{35}{84}+\dfrac{-9}{84}=\dfrac{35+\left(-9\right)}{84}=\dfrac{26}{84}=\dfrac{13}{42}\)
c. \(\dfrac{-7}{15}+\dfrac{3}{35}=\dfrac{-49}{105}+\dfrac{9}{105}=\dfrac{-49+9}{105}=\dfrac{-40}{105}=\dfrac{-8}{21}\)
d. \(\dfrac{-5}{7}+\dfrac{-3}{4}=\dfrac{-20}{28}+\dfrac{-21}{28}=\dfrac{-20+\left(-21\right)}{28}=\dfrac{-41}{28}\)
a: \(=\dfrac{1}{3}\cdot\dfrac{1}{3}\cdot\dfrac{-17}{18}\cdot\dfrac{14}{17}=\dfrac{-14}{18\cdot9}=\dfrac{-14}{162}=\dfrac{-7}{81}\)
b: \(=\dfrac{12}{4}+\dfrac{35}{11}\cdot\dfrac{121}{245}=3+\dfrac{11}{7}=\dfrac{32}{7}\)
a: \(=\dfrac{15}{135}\cdot\dfrac{-17}{18}\cdot\dfrac{14}{17}=\dfrac{1}{9}\cdot\dfrac{-7}{9}=\dfrac{-7}{81}\)
b: \(=3+\dfrac{35}{11}\cdot\dfrac{121}{245}=3+\dfrac{11}{7}=\dfrac{32}{7}\)
\(\Rightarrow\dfrac{15}{x}=\dfrac{7}{28}-\dfrac{3}{4}\\ \Rightarrow\dfrac{15}{x}=\dfrac{-2}{4}\\ \Rightarrow15.4=x.\left(-2\right)=60\\ \Rightarrow x=60:\left(-2\right)=-30\\ \Rightarrow x=-30\)
\(=\dfrac{5\cdot1\cdot\left(-4\right)\cdot7}{14\cdot3\cdot15\cdot5}=\dfrac{\left(-4\right)}{2\cdot3\cdot15}=\dfrac{-4}{90}=-\dfrac{2}{45}\)
a: \(x\cdot\dfrac{3}{4}+x=\dfrac{7}{8}\)
\(\Leftrightarrow x\cdot\dfrac{7}{4}=\dfrac{7}{8}\)
\(\Leftrightarrow x=\dfrac{1}{2}\)
\(=-\dfrac{1}{5}\cdot\dfrac{3}{4}=-\dfrac{3}{20}\)