Answer:
The digit "3" represent the rate at which the population of rabbits is increasing.
i.e. it represents the rate at which the population of rabbits triples each year.
Explanation:
It is given that:
The population of a species of rabbit triples every year.
The function which is used to represent the this function i.e. the modelling function is given by:
![f(x)=4\cdot 3^x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/fhty8anag7ai1sltxrpl9yl6ef09c4d8x5.png)
where x represent the number of year.
Also,
![f(5) = 972](https://img.qammunity.org/2019/formulas/mathematics/middle-school/sk1v32n0g9d8rhl0csjjeh41gv1ji1e74c.png)
We know that the exponential function is given by:
![f(x)=ab^x](https://img.qammunity.org/2019/formulas/mathematics/college/7d3bhz3s0mj9sitvy232vyy8ripkz9rp03.png)
where a is the initial population and b is the rate at which the function increases or decreases.