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Algebra Difficulty 4.7 AIME Find the answer

Evaluate 2016!22015!2017!\frac{2016!^{2}}{2015!2017!}. Here nn ! denotes 1×2××n1 \times 2 \times \cdots \times n.

A number or a short expression. Spacing and $ signs are ignored.

Solution

2016!22015!2017!=2016!2015!2016!2017!=2016112017=20162017\frac{2016!^{2}}{2015!2017!}=\frac{2016!}{2015!} \frac{2016!}{2017!}=\frac{2016}{1} \frac{1}{2017}=\frac{2016}{2017}

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