Answer:
To determine the intervals on the y-axis where a nonconstant solution y = ϕ(x) is increasing or decreasing, we need the differential equation that describes the behavior of ϕ(x). Without the specific differential equation, it is not possible to provide the intervals.
Please provide the differential equation so that I can assist you further in determining the intervals of increase and decrease on the y-axis for the solution ϕ(x).