4.190 Выполните сложение: 4 2 a) - + (-); 7 7 3 3 6) - + (-): 7 4 5 B)-+(-7); 9 8 2 2 г) -2 - + (-5 -); 9 18 3 3 д) -3 - + (-5,9); 5 1 e) -2 -+(-4,75).

Ответ: a) -6/7; б) -33/28; в) -125/72; г) -7 1/18; д) -9,5; e) -6,91(6)

1. a) \[-\frac{4}{7} + \left(-\frac{2}{7}\right) = -\frac{4}{7} - \frac{2}{7} = -\frac{4+2}{7} = -\frac{6}{7}\]
2. б) \[-\frac{3}{7} + \left(-\frac{3}{4}\right) = -\frac{3}{7} - \frac{3}{4} = -\frac{3 \cdot 4}{7 \cdot 4} - \frac{3 \cdot 7}{4 \cdot 7} = -\frac{12}{28} - \frac{21}{28} = -\frac{12+21}{28} = -\frac{33}{28}\]
3. в) \[-\frac{5}{9} + \left(-\frac{7}{8}\right) = -\frac{5}{9} - \frac{7}{8} = -\frac{5 \cdot 8}{9 \cdot 8} - \frac{7 \cdot 9}{8 \cdot 9} = -\frac{40}{72} - \frac{63}{72} = -\frac{40+63}{72} = -\frac{103}{72} = -1\frac{31}{72}\]
4. г) \[-2\frac{2}{9} + \left(-5\frac{5}{18}\right) = -2\frac{2}{9} - 5\frac{5}{18} = -2\frac{2 \cdot 2}{9 \cdot 2} - 5\frac{5}{18} = -2\frac{4}{18} - 5\frac{5}{18} = -(2\frac{4}{18} + 5\frac{5}{18}) = -7\frac{9}{18} = -7\frac{1}{2}\]
5. д) \[-3\frac{3}{5} + (-5,9) = -3,6 - 5,9 = -(3,6 + 5,9) = -9,5\]
6. e) \[-2\frac{1}{6} + (-4,75) = -2,1666... - 4,75 = -(2,1666... + 4,75) = -6,91(6)\]

Ответ: a) -6/7; б) -33/28; в) -125/72; г) -7 1/18; д) -9,5; e) -6,91(6)