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Harvard-MIT Mathematics Tournament #0j3y

Harvard-MIT Mathematics TournamentHard

From module Newton's Sums

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Understand the scale
Scale 0.5: Easiest math competition problems, often solvable even for early middle school students without experience. 1: Problems strictly for beginners, often at a moderate middle school level. 1.5: Problems for stronger beginner students, on the level of the middling problems in most middle school contests. 2: For motivated beginners, harder questions from the previous categories. 2.5: More advanced beginner problems, hardest questions from previous categories. 3: Early intermediate problems that require more creative thinking. 3.5: Tougher early intermediate problems that consistently stretch into higher-level creative thinking or conceptual knowledge. 4: Intermediate-level problems. 4.5: Upper intermediate problems approaching the upper bound for non-invitational sprint math competitions. 5: More difficult AIME problems or simple proof-based Olympiad-style problems. 6: High-level AIME-styled questions or introductory Olympiad-level questions. 7: Tougher Olympiad-level questions, may require more technical knowledge. 8: High-level Olympiad-level questions. 9: Expert Olympiad-level questions. 9.5: The hardest problems appearing on Olympiads which the strongest students could reasonably solve. 10: Historically notorious problems, generally unsuitable for even very hard competitions because they are exceedingly tedious, long, and difficult.
OtherPolynomial interpolation: Newton, LagrangeIntegers

Problem

Problem:

Let SS be the set of ordered pairs of integers (x,y)(x, y) with 1≤x≤51 \leq x \leq 5 and 1≤y≤31 \leq y \leq 3. How many subsets RR of SS have the property that all the points of RR lie on the graph of a single cubic? A cubic is a polynomial of the form y=ax3+bx2+cx+dy=a x^{3}+b x^{2}+c x+d, where a,b,ca, b, c, and dd are real numbers (meaning that aa is allowed to be 0 ).

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