Question

A=[-∞;0] a*b=ab Помогите плиз

Answer 1

Знак умножения. Т.к ab с минусом, то подойдут любые значения от (-∞;-1]
Допустим: 
-1*1=-1
-10*2=-20
Если подставить за место a - 0, то выражение получится равное 0 - не подходит по условию
Надеюсь я так понял задание)

Answer 2

Solving the Equation A=[-∞;0]

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