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Harvard-MIT November Tournament #0izf

Harvard-MIT November 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.
Polynomial interpolation: Newton, LagrangeInduction / smoothing

Problem

Problem: A function f(x1,x2,…,xn)f\left(x_{1}, x_{2}, \ldots, x_{n}\right) is linear in each of the xix_{i} and f(x1,x2,…,xn)=1x1x2⋯xnf\left(x_{1}, x_{2}, \ldots, x_{n}\right)=\frac{1}{x_{1} x_{2} \cdots x_{n}} when xi∈{3,4}x_{i} \in\{3,4\} for all ii. In terms of nn, what is f(5,5,…,5)f(5,5, \ldots, 5)?

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