The condition of positive value of fraction: (denominator ≠ 0) the condition of negative value:

The condition of positive value of fraction: (denominator ≠ 0) the condition of negative value:

The condition of positive value of fraction: numerator × denominator > 0 (denominator ≠ 0)
The condition of negative value: numerator × denominator < 0 (denominator ≠ 0)