Maths Olympiad Prep

Track / Stage 3 / 166 of 260 #166 of 1964

Problem 166

AMC 10/12, early questions
Algebra Difficulty 3.4 Find the answer

Given the function f(x)=x21f(x)=x^{2}-1 with domain DD and range {0,1}\{0,1\}, determine the maximum number of such sets DD.

A number or a short expression. Spacing and $ signs are ignored.

Official solution

Since f(x)=x21f(x)=x^{2}-1,

We have f(±1)=0f(±1)=0 and f(±2)=1f(± \sqrt {2})=1.

Therefore, the possible domains DD are: {1,2}\{1, \sqrt {2}\}, {1,2}\{-1,- \sqrt {2}\}, {1,2}\{-1, \sqrt {2}\}, {1,2}\{1,- \sqrt {2}\}, {1,1,2}\{-1,1, \sqrt {2}\}, {1,1,2}\{-1,1,- \sqrt {2}\}, {1,2,2}\{1, \sqrt {2},- \sqrt {2}\}, {1,2,2}\{-1, \sqrt {2},- \sqrt {2}\}, and {1,1,2,2}\{-1,1, \sqrt {2},- \sqrt {2}\}, making a total of 99 cases.

Hence, the answer is 9\boxed{9}.

To solve this problem, we inferred potential xx-values in the domain based on the given function expression and the values in the range. Then, we combined these xx-values to find the various possibilities for domain DD. This question primarily assesses your understanding of functions and the ability to make simple deductions, making it a foundational problem.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.