Краткое пояснение:
Необходимо определить знак коэффициента в каждом выражении.
a) a ⋅ (−b) ⋅ (−c) ⋅ d = a ⋅ (−1)b ⋅ (−1)c ⋅ d = (−1) ⋅ (−1) ⋅ a ⋅ b ⋅ c ⋅ d = abcd. Знак коэффициента: +
б) −4a ⋅ (−3b) ⋅ (−2c) ⋅ (−5) = (−4) ⋅ (−3) ⋅ (−2) ⋅ (−5) ⋅ a ⋅ b ⋅ c = 120abc. Знак коэффициента: +
в) −4a ⋅ 5b ⋅ (−0,4c) = (−4) ⋅ 5 ⋅ (−0,4) ⋅ a ⋅ b ⋅ c = 8abc. Знак коэффициента: +
Ответ: смотри решение выше