a_n = 2^n + 3
the first differences have a geometric progression, so the explicit definition will be an exponential function. (it cannot be modeled by a linear or quadratic function.) the above answer is the only choice that is an exponential function.
first differences are
(7-5=)2, 4, 8, 16
5, 7, 11, 19,
write an explicit definition that de...