Контрольные задания > Сравните произведения: а) 14 ⋅ 15 и 15 ⋅ 14; б) 2 ⋅ 3 ⋅ 4 ⋅ 5 и 6 ⋅ 21; в) 3 ⋅ (4 + 12) и (4 + 8) ⋅ 4; г) 7x и 0 ⋅ x.
Вопрос:

Сравните произведения: а) 14 ⋅ 15 и 15 ⋅ 14; б) 2 ⋅ 3 ⋅ 4 ⋅ 5 и 6 ⋅ 21; в) 3 ⋅ (4 + 12) и (4 + 8) ⋅ 4; г) 7x и 0 ⋅ x.

Ответ:

  • а) 14 ⋅ 15 = 15 ⋅ 14 (от перестановки мест множителей произведение не меняется).
  • б) 2 ⋅ 3 ⋅ 4 ⋅ 5 = 120 и 6 ⋅ 21 = 126. Следовательно, 2 ⋅ 3 ⋅ 4 ⋅ 5 < 6 ⋅ 21.
  • в) 3 ⋅ (4 + 12) = 3 ⋅ 16 = 48 и (4 + 8) ⋅ 4 = 12 ⋅ 4 = 48. Следовательно, 3 ⋅ (4 + 12) = (4 + 8) ⋅ 4.
  • г) 7x и 0 ⋅ x = 0. Если x ≠ 0, то 7x > 0. Если x = 0, то 7x = 0. Следовательно, при x ≠ 0, 7x > 0 ⋅ x; при x = 0, 7x = 0 ⋅ x.
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