Final answer:
The correct equation for the probiotic is dN₂/dt=r₂N₂(1-N₂+a21N₁/K₂). It represents the logistic growth model and considers various factors such as the growth rate, population sizes, and competitive effects.
Step-by-step explanation:
In the equation provided, the correct equation for the probiotic is:
dN₂/dt=r₂N₂(1-N₂+a21N₁/K₂)
This equation represents the logistic growth model, where dN₂/dt represents the rate of change of the probiotic population over time, r₂ is the growth rate of the probiotic, N₂ is the current population size of the probiotic, N₁ represents the population size of the pathogen, a21 is the competitive effect of the pathogen on the probiotic, and K₂ is the carrying capacity of the probiotic population.