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Find the number of positive integers `n` such that 105 is a divisor of `n^(2)+n+1` |
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Answer» The digit in the unit place of `n(n+1)+1` is 1,3, or 7 `implies` 5 does not divides `n^(2)+n+1` `implies` 105 is not a divisor of `n(n+1)+1`, |
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