• 842. Выполните действия: a)-31.(-1); 5 4 1-1-7 B)()--:-1. (--); 7 21 6 2-3 6) -8-.(26):(-9)2; r)-2-).(32)

Ответ: a) -\frac{4}{5}; б) 2; в) -\frac{10}{9}; г) \frac{17}{18}.

• а)\[-3\frac{1}{5} \cdot \left(-\frac{1}{4}\right)^2 = -\frac{16}{5} \cdot \frac{1}{16} = -\frac{1}{5}\]
• б)\[-8\frac{2}{3} \cdot \left(-\frac{1}{26}\right) : \left(-\frac{7}{9}\right)^2 = -\frac{26}{3} \cdot \left(-\frac{1}{26}\right) : \frac{49}{81} = \frac{1}{3} \cdot \frac{81}{49} = \frac{27}{49}\]
• в)\[\left(1\frac{1}{7}\right)^2 : 1\frac{19}{21} \cdot \left(-\frac{5}{6}\right) = \left(\frac{8}{7}\right)^2 : \frac{40}{21} \cdot \left(-\frac{5}{6}\right) = \frac{64}{49} \cdot \frac{21}{40} \cdot \left(-\frac{5}{6}\right) = \frac{16}{7} \cdot \frac{3}{10} \cdot \left(-\frac{5}{6}\right) = \frac{8}{7} \cdot \frac{3}{5} \cdot \left(-\frac{5}{3}\right) = -\frac{8}{7}\]
• г)\[\left(-\frac{2}{3}\right)^3 \cdot \left(-2\frac{17}{32}\right) = -\frac{8}{27} \cdot \left(-\frac{81}{32}\right) = \frac{1}{1} \cdot \frac{3}{4} = \frac{3}{4}\]

Ответ: a) -\frac{4}{5}; б) 2; в) -\frac{10}{9}; г) \frac{17}{18}.