∣xy∣=∣x∣∣y∣|x y|=|x||y|∣xy∣=∣x∣∣y∣
∣xy∣<∣x∣∣y∣|x y|<|x||y|∣xy∣<∣x∣∣y∣
∣xy∣>∣x∣∣y∣|x y|>|x||y|∣xy∣>∣x∣∣y∣
∣xy∣≤∣x∣∣y∣|x y| \leq|x||y|∣xy∣≤∣x∣∣y∣