Suppose that 21×32×43×54×⋯×nn−1=81. What is the value of n?
A number or a short expression. Spacing and $ signs are ignored.
Solution
Since 21×32×43×54×⋯×nn−1=81, then squaring both sides, we obtain 21×32×43×54×⋯×nn−1=641. Simplifying the left side, we obtain 2×3×4×5×⋯×n1×2×3×4×⋯×(n−1)=641 or (2×3×4×⋯×(n−1))×n1×(2×3×4×⋯×(n−1))=641 and so n1=641 which means that n=64.
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