From the given question we come to know of certain number of facts and they are: At 1:00 PM the water level of the pond was = 13 inches At 1:30 PM the water level of the pond was = 18 inches At 2:30 PM the water level of the pond was = 28 inches From the above given facts we can easily find the amount of water changing every half an hour. Amount of increase in water from 1:00PM to 1:30 PM = (18 - 13) inches = 5 inches Amount of increase in water level from 1:30PM to 2:30PM = (28 -18) inches = 10 inches From the above two deductions we can come to the conclusion the the constant rate of change in water level is 5 inches for every half an hour.
To be a function for every identical x value it has to have a different Y value. If the set has two identical X values but they have different Y values it can't be a function.
