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Divisibility (Posted on 2004-01-06) Difficulty: 3 of 5
For how many natural numbers x, is the expression: (x ² + 2x + 3) divisible by 35 ?

  Submitted by Ravi Raja    
Rating: 2.5000 (6 votes)
Solution: (Hide)
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.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re: Simplest solution - no moduli!Steve Herman2016-06-11 08:15:09
Simplest solution - no moduli!JayDeeKay2016-06-10 10:23:34
SolutionAlternative MethodologyK Sengupta2007-11-29 11:12:38
Solutionummpaul2004-03-24 22:41:59
re: SemanticsRavi Raja2004-01-16 02:45:36
Solutiona bit clearerzaphod2004-01-07 03:19:36
re(3): SolutionGamer2004-01-06 20:24:43
re(2): SolutionCharlie2004-01-06 13:18:15
re: SolutionSilverKnight2004-01-06 11:38:28
SolutionSemanticsDan Blume2004-01-06 11:30:11
SolutionBrian Smith2004-01-06 10:56:19
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