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MathNet 2017-part-07 — 172 problems (EN–VI) Question 5

Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)

Question 5

Consider all ordered pairs of integers $(a, b)$ such that $1 \leq a \leq b \leq 100$ and
$$
\frac{(a+b)(a+b+1)}{a b}
$$
is an integer.
Among these pairs, find the one with largest value of $b$. If multiple pairs have this maximal value of $b$, choose the one with largest $a$. For example choose $(3,85)$ over $(2,85)$ over $(4,84)$. Note that your answer should be an ordered pair.