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IMO 1969 - Longlist Problems Question 56

IMO Shortlist · IMO 1969 - Longlist Problems

Question 56

(POL 5) Let $a$ and $b$ be two natural numbers that have an equal number $n$ of digits in their decimal expansions. The first $m$ digits (from left to right) of the numbers $a$ and $b$ are equal. Prove that if $m \gt n/2$, then
$$ a^{1/n}-b^{1/n} \lt \frac1n. $$