ITOT 43 Autumn 2021 - THPT A - additive practice Question 4

Find the smallest real number $k$ such that among any three nonzero real numbers there are two, $a,b$, with
$$|a-b|\le k\quad\text{or}\quad\left|\frac1a-\frac1b\right|\le k.$$
(7 points)



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