Краткое пояснение: Применяем распределительное свойство умножения: выносим общий множитель за скобки.
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a) 8 ⋅ 4 + 8 ⋅ 16 = 8 ⋅ (4 + 16) = 8 ⋅ 20 = 160
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б) 39 ⋅ 23 - 29 ⋅ 23 = 23 ⋅ (39 - 29) = 23 ⋅ 10 = 230
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в) 5 ⋅ 13 + 15 ⋅ 13 = 13 ⋅ (5 + 15) = 13 ⋅ 20 = 260
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г) 7 ⋅ 21 - 2 ⋅ 21 = 21 ⋅ (7 - 2) = 21 ⋅ 5 = 105
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д) 2,4 ⋅ 21 + 2,4 ⋅ 9 = 2,4 ⋅ (21 + 9) = 2,4 ⋅ 30 = 72
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е) 1,4 ⋅ 0,6 – 0,6 ⋅ 0,6 = 0,6 ⋅ (1,4 - 0,6) = 0,6 ⋅ 0,8 = 0,48
Ответ: a) 160; б) 230; в) 260; г) 105; д) 72; е) 0,48