№3. Вычислите: 1) -14 + 9; 2) 28 + (-5); 3) -21 - 16; 4) -19 – (-81); 5) – 2,5 – 1,9; 6) – \frac{3}{16} + \frac{5}{12}; 7) – \frac{10}{11} – (– \frac{10}{11}); 8) 1\frac{2}{9} + (– \frac{11}{27}). №4. Решите уравнения: 1) 21 + x = 8; 2) x – 4,5 = –8,8; 3) – 11,8 – x = –4,6. №5. Вычислите: 1) \frac{13}{30} – (– \frac{1}{6}) + (– \frac{7}{10}) – \frac{11}{15}; 2) – (– \frac{1}{2}) – \frac{47}{50} – \frac{2}{5} + (– \frac{3}{10}); 3) – \frac{23}{44} – \frac{1}{2} + \frac{3}{4} + \frac{31}{88} + \frac{9}{11}; 4) – \frac{13}{46} – \frac{3}{4} – \frac{61}{120} + \frac{11}{30} – \frac{7}{12}.

Решение №3

1) \(-14 + 9 = -5\) 2) \(28 + (-5) = 28 - 5 = 23\) 3) \(-21 - 16 = -37\) 4) \(-19 - (-81) = -19 + 81 = 62\) 5) \(-2.5 - 1.9 = -4.4\) 6) \(-\frac{3}{16} + \frac{5}{12} = -\frac{3 \cdot 3}{16 \cdot 3} + \frac{5 \cdot 4}{12 \cdot 4} = -\frac{9}{48} + \frac{20}{48} = \frac{11}{48}\) 7) \(-\frac{10}{11} - (-\frac{10}{11}) = -\frac{10}{11} + \frac{10}{11} = 0\) 8) \(1\frac{2}{9} + (-\frac{11}{27}) = \frac{11}{9} - \frac{11}{27} = \frac{11 \cdot 3}{9 \cdot 3} - \frac{11}{27} = \frac{33}{27} - \frac{11}{27} = \frac{22}{27}\)

Решение №4

1) \(21 + x = 8\) \(x = 8 - 21\) \(x = -13\) 2) \(x - 4.5 = -8.8\) \(x = -8.8 + 4.5\) \(x = -4.3\) 3) \(-11.8 - x = -4.6\) \(-x = -4.6 + 11.8\) \(-x = 7.2\) \(x = -7.2\)

Решение №5

1) \(\frac{13}{30} - (-\frac{1}{6}) + (-\frac{7}{10}) - \frac{11}{15} = \frac{13}{30} + \frac{1}{6} - \frac{7}{10} - \frac{11}{15} = \frac{13}{30} + \frac{5}{30} - \frac{21}{30} - \frac{22}{30} = \frac{13 + 5 - 21 - 22}{30} = \frac{-25}{30} = -\frac{5}{6}\) 2) \(-(-\frac{1}{2}) - \frac{47}{50} - \frac{2}{5} + (-\frac{3}{10}) = \frac{1}{2} - \frac{47}{50} - \frac{2}{5} - \frac{3}{10} = \frac{25}{50} - \frac{47}{50} - \frac{20}{50} - \frac{15}{50} = \frac{25 - 47 - 20 - 15}{50} = \frac{-57}{50} = -1\frac{7}{50}\) 3) \(-\frac{23}{44} - \frac{1}{2} + \frac{3}{4} + \frac{31}{88} + \frac{9}{11} = -\frac{46}{88} - \frac{44}{88} + \frac{66}{88} + \frac{31}{88} + \frac{72}{88} = \frac{-46 - 44 + 66 + 31 + 72}{88} = \frac{79}{88}\) 4) \(-\frac{13}{46} - \frac{3}{4} - \frac{61}{120} + \frac{11}{30} - \frac{7}{12} = -\frac{13 \cdot 60}{46 \cdot 60} - \frac{3 \cdot 345}{4 \cdot 345} - \frac{61 \cdot 23}{120 \cdot 23} + \frac{11 \cdot 92}{30 \cdot 92} - \frac{7 \cdot 115}{12 \cdot 115} = \frac{-780 - 1035 - 1403 + 1012 - 805}{1380} = \frac{-3000 - 1035 - 1403 + 1012 - 805 + 217}{1380} = -\frac{3391}{1380} \approx -2.457\)

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