Mathematical Models
Given a set of two-variable data, we can tell if there is a linear relationship between them by analyzing the change of values of y with respect to the change of values of x.
If the relationship was linear, the change in values of y should be the same when the change in x is equal.
Note that between 2016 and 2017 there was only one year and the value of the house increased by $20,000.
For the next two years, the value increased by $21,000. This means the relationship is not linear.
The possible exponential relationship is also easy to spot. If the ratio between the values of y is constant, then it's an exponential function.
Testing the ratios:
420,000 / 400,000 = 1.05
441,000 / 420,000 = 1.05
463,050 / 441,000 = 1.05
Since the ratio is constant, the growth can be modeled with an exponential function.