№8. Выполните действия: 1)-15,3 0,8 + 3,7 (-1,8); 2) (-6,14 + 6,07) (3,4 – 4); 3) 8/9 (-3 9/16) - 4 5/6 (-7/58); 4) (3 5/6-412) (3 4/5 - 0.55).

Ответ:

1) \[ -15.3 \cdot 0.8 + 3.7 \cdot (-1.8) = -12.24 - 6.66 = -18.9 \]

2) \[ (-6.14 + 6.07) \cdot (3.4 - 4) = -0.07 \cdot (-0.6) = 0.042 \]

3) \[ \frac{8}{9} \cdot (-3\frac{9}{16}) - 4\frac{5}{6} \cdot (-\frac{7}{58}) = \frac{8}{9} \cdot (-\frac{57}{16}) - \frac{29}{6} \cdot (-\frac{7}{58}) = -\frac{1 \cdot 19}{3 \cdot 2} + \frac{29 \cdot 7}{6 \cdot 58} = -\frac{19}{6} + \frac{1 \cdot 7}{6 \cdot 2} = -\frac{19}{6} + \frac{7}{12} = -\frac{38}{12} + \frac{7}{12} = -\frac{31}{12} = -2\frac{7}{12} \]

4) \[ (3\frac{5}{6} - 4\frac{1}{2}) \cdot (3\frac{4}{5} - 0.55) = (\frac{23}{6} - \frac{9}{2}) \cdot (\frac{19}{5} - \frac{55}{100}) = (\frac{23}{6} - \frac{27}{6}) \cdot (\frac{19}{5} - \frac{11}{20}) = -\frac{4}{6} \cdot (\frac{76}{20} - \frac{11}{20}) = -\frac{2}{3} \cdot \frac{65}{20} = -\frac{2}{3} \cdot \frac{13}{4} = -\frac{1 \cdot 13}{3 \cdot 2} = -\frac{13}{6} = -2\frac{1}{6} \]

Ответ: 1) -18.9; 2) 0.042; 3) \[ -2\frac{7}{12} \]; 4) \[ -2\frac{1}{6} \]