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Divisibility (Posted on 2004-01-06) |
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For how many natural numbers x, is the expression: (x ² + 2x + 3) divisible by 35 ?
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Submitted by Ravi Raja
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Rating: 2.5000 (6 votes)
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Solution:
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(Hide)
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The number x can take the values from 0 to 9 or any other value ending in these digits.
Now, x ² will always end in: 0, 1, 4, 5, 6, or 9.
So, (x ² + 2x) will end in: 0, 3, 4, 5,or 8.
Therefore, (x ² + 2x + 3) will always end in: 1, 2, 3, 6, 7, or 8.
Since in none of the cases the last digit is a 0 or a 5, hence it is not divisible by 5 and therefore never by 35 implying that there does not exist any natural number x such that (x ² + 2x + 3) will be divisible by 35 without leaving any remainder.
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