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MathNet 2013 Question 40

Math Olympiad Vault · MathNet 2013

Question 40

Do there exist real numbers $a,b,c,d\gt 0$ and $e,f,g,h\lt 0$ satisfying simultaneously
$$ae+bc\gt 0,\quad ef+cg\gt 0,\quad fd+gh\gt 0,\quad da+hb\gt 0?$$