The function g = 4r 30 describes how many gallons (g) of water are in a reservoir at any time. 30 gallons of water are currently in the reservoir. Water is added to the reservoir at a rate (r) of 4 gallons per minute.
The function g = 4r + 30 describes how many gallons of water are in a reservoir at any time. Initially, 30 gallons of water are in the reservoir. Water is added to the reservoir at a constant rate of 4 gallons per minute.
