Answer: The refrigerator cost in this month is $4.5 approximately.
Step-by-step explanation:
Since we have given that
Amount of watt of electric power = 320 W
Number of days = 30
Unit cost of electricity = $0.13/Kwh
Hold factor = 
Number of hours in a month = 24
So, the refrigerator cost in this month would be

Hence, the refrigerator cost in this month is $4.5 approximately.
Yes they are equivalent expressions. If you take the z to the power of two, and subtract that from the other z to the power of two, it is zero. So you are left with four which is the answer
Step-by-step explanation:
Probability of an event is 1
and probability of non event is 0