To find a graph in which the parks can predict when there will be no change in the water level, we will use x^2-1 as our function. To find the levels in which water does not equal zero we will have to set it equal to zero. so in this case we could factor to get x+1 * x-1 then we now have to find when x=0 which is at x=1 and x-1. At these points the water level will not be changing