nicolietavares
15

# Efetue os cálculos indicados nas expressões numéricas: a) 3/5 x (1/3 - 1/2) b) - 2/9 x (1/4 + 1/5) , c)2/5 - 8/3 x (1/2)³ +3/4 , d) -7/9 x (2/3 - 4/5 x 5)

(1) Respostas
a) Temos que:   $\dfrac{3}{5}\times\left(\dfrac{1}{3}-\dfrac{1}{2}\right)$   $=\dfrac{3}{5}\times\left(\dfrac{2-3}{6}\right)$   $=\dfrac{3}{5}\times\dfrac{-1}{6}=\dfrac{-3}{30}=\dfrac{-1}{10}$ b) Temos que:   $\dfrac{-2}{9}\times\left(\dfrac{1}{4}+\dfrac{1}{5}\right)$   $=\dfrac{-2}{9}\times\left(\dfrac{5+4}{20}\right)$   $=\dfrac{-2}{9}\times\dfrac{9}{20}=\dfrac{-18}{180}=\dfrac{-1}{10}$   c) Temos que:   $\dfrac{2}{5}-\dfrac{8}{3}\times\left(\dfrac{1}{2}\right)^3+\dfrac{3}{4}$   $=\dfrac{2}{5}-\dfrac{8}{3}\times\dfrac{1}{8}+\dfrac{3}{4}$   $=\dfrac{2}{5}-\dfrac{1}{3}+\dfrac{3}{4}$   $=\dfrac{24-20+45}{60}=\dfrac{49}{60}$ d) Temos que:   $\dfrac{-7}{9}\times\left(\dfrac{2}{3}-\dfrac{4}{5}\times5\right)$   $=\dfrac{-7}{9}\times\left(\dfrac{2}{3}-4\right)$   $=\dfrac{-7}{9}\times\left(\dfrac{2-12}{12}\right)$   $=\dfrac{-7}{9}\times\dfrac{-10}{12}$   $=\dfrac{70}{108}=\dfrac{35}{54}$