4.280 Выполните умножение: а) - 4/5 ⋅ 5/8; б) - 4/9 ⋅ (15/26); д) - 5/12 ⋅ 18; с) - 10 ⋅ (- 7/9)

Ответ: a) -1/2; б) -10/39; д) -15/2; с) 70/9

• a) \[-\frac{4}{5} \cdot \frac{5}{8} = -\frac{4 \cdot 5}{5 \cdot 8} = -\frac{4}{8} = -\frac{1}{2}\]
• б) \[-\frac{4}{9} \cdot \frac{15}{26} = -\frac{4 \cdot 15}{9 \cdot 26} = -\frac{2 \cdot 5}{3 \cdot 13} = -\frac{10}{39}\]
• д) \[-\frac{5}{12} \cdot 18 = -\frac{5 \cdot 18}{12} = -\frac{5 \cdot 3}{2} = -\frac{15}{2}\]
• c) \[-10 \cdot \left(-\frac{7}{9}\right) = \frac{10 \cdot 7}{9} = \frac{70}{9}\]

Ответ: a) -1/2; б) -10/39; д) -15/2; с) 70/9