N3. Найти значение выражения: 1) 15,6 · 2,8 + 19,5 · 2,4 – 15,6 · 5,8 – 19,5 · 7,4 ; 2) 5\frac{5}{8} \cdot 8\frac{5}{8} – 4\frac{1}{2} + \frac{1}{6} + 6\frac{5}{8} \cdot 8\frac{5}{8} – 7\frac{3}{5} \cdot 1\frac{1}{6}.

Решение:

1) \(15.6 \cdot 2.8 + 19.5 \cdot 2.4 - 15.6 \cdot 5.8 - 19.5 \cdot 7.4 = 15.6 \cdot (2.8 - 5.8) + 19.5 \cdot (2.4 - 7.4) = 15.6 \cdot (-3) + 19.5 \cdot (-5) = -46.8 - 97.5 = -144.3\) 2) \(5\frac{5}{8} \cdot 8\frac{5}{8} - 4\frac{1}{2} + \frac{1}{6} + 6\frac{5}{8} \cdot 8\frac{5}{8} - 7\frac{3}{5} \cdot 1\frac{1}{6} = (5\frac{5}{8} + 6\frac{5}{8}) \cdot 8\frac{5}{8} - 4\frac{1}{2} + \frac{1}{6} - 7\frac{3}{5} \cdot 1\frac{1}{6} = 12\frac{10}{8} \cdot 8\frac{5}{8} - 4\frac{1}{2} + \frac{1}{6} - 7\frac{3}{5} \cdot 1\frac{1}{6} = 13\frac{1}{4} \cdot 8\frac{5}{8} - 4\frac{1}{2} + \frac{1}{6} - 7\frac{3}{5} \cdot 1\frac{1}{6} = \frac{53}{4} \cdot \frac{69}{8} - \frac{9}{2} + \frac{1}{6} - \frac{38}{5} \cdot \frac{7}{6} = \frac{3657}{32} - \frac{9}{2} + \frac{1}{6} - \frac{266}{30} = \frac{3657}{32} - \frac{144}{32} + \frac{1}{6} - \frac{266}{30} = \frac{3513}{32} + \frac{5}{30} - \frac{266}{30} = \frac{3513}{32} - \frac{261}{30} = \frac{3513}{32} - \frac{87}{10} = \frac{17565}{160} - \frac{1392}{160} = \frac{16173}{160} = 101.08125\)