a) none of the offered choices
b) none of the offered choices
c) quadratic
d) exponential
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When the given x-values are equally-spaced, one can look at first and second differences.
.. If first differences are constant, the relation is linear.
.. If second differences are constant, the relation is quadratic.
.. If second differences match first differences, the relation is exponential.
Otherwise, the relation can be modeled by a polynomial of degree equal to the number of points minus 1. Sometimes, you can guess the relationship from a graph, or use regression techniques to model it.
