2025 AMC 10A Problem 9

Attempt Problem 9 of the 2025 AMC 10A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2025 AMC 10A solutions, or check the answer key.

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9.

Let f(x)=100x3300x2+200x.f(x) = 100x^3 - 300x^2 + 200x. For how many real numbers aa does the graph of y=f(xa)y = f(x - a) pass through the point (1,25)?(1, 25)?

11

22

33

44

more than 44

Answer: C
Concepts:functionpolynomial
Difficulty rating: 1440
Solution:

The graph passes through (1,25)(1,25) exactly when f(1a)=25.f(1 - a) = 25. Let t=1a,t = 1 - a, so we count solutions of f(t)=25.f(t) = 25. Factor f(x)=100x(x1)(x2),f(x) = 100x(x-1)(x-2), with roots 0,1,2.0, 1, 2. On (0,1),(0,1), the function is positive and f(0.5)=37.5>25,f(0.5) = 37.5 \gt 25, so continuity gives one root on each side of 0.5.0.5. On (1,2)(1,2) the function is negative, while for x>2x \gt 2 it increases from 00 to infinity, giving one more root. A cubic equation has at most 33 real roots, so these are all the solutions. Each gives one a,a, so there are 33 values. Thus, C is the correct answer.

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