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China Second Round Olympiad 2023 Test 1 Q 11

Source: Sep 10, 2023

September 10, 2023
inequalities proposedalgebraChinainequalities

Problem Statement

Find all real numbers t t not less than 11 that satisfy the following requirements: for any a,b∈[−1,t]a,b\in [-1,t] , there always exists c,d∈[−1,t]c,d \in [-1,t ] such that (a+c)(b+d)=1. (a+c)(b+d)=1.
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