Problem of the Month
Problem 3: December 2019
Let a, b, c, and d be rational numbers and f (x) = ax3 + bx2 + cx + d. Suppose
f (n) is an integer whenever n is an integer and that
1 3 2 1 4
n − n − ≤ f (n) ≤ n3 + n2 + 2n +
3 3 3 3
for every integer n with the possible exception of n = −2.
1
(a) Show that a = .
3
(b) Find f (102019 ) − f (102019 − 1).
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