1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B A question regarding multiples of 3

  1. Dec 20, 2016 #1
    Why doesn't any odd multiple of 3 can give "24-1(x2-1)=y" as a result (y) a natural number? Obviously no even number will make "y" a natural number, but all of the odd numbers do, but odd multiples of 3 (3, 9, 15, 21, 27...).

    x=1⇒y=0
    x=3⇒y=1/3
    x=5⇒y=1
    x=7⇒y=2
    x=9⇒y=10/3
    x=11⇒y=5
    x=13⇒y=7
    x=15⇒y=28/3
    x=17⇒y=12
    x=19⇒y=15
    x=21⇒y=55/3
    .
    .
    .
     
    Last edited: Dec 20, 2016
  2. jcsd
  3. Dec 20, 2016 #2

    jedishrfu

    Staff: Mentor

    Can you explain this better perhaps by using an example?
     
  4. Dec 20, 2016 #3
    I'm sorry, I typed it wrongly, it's not "1/2", it's "1/24".
     
  5. Dec 20, 2016 #4

    jedishrfu

    Staff: Mentor

    Okay, but can you explain this better perhaps by using an example?

    Is this a homework assignment?
     
  6. Dec 20, 2016 #5
    There, now I think it's WAY better understandable. I'm sorry. Lol
     
  7. Dec 20, 2016 #6

    TeethWhitener

    User Avatar
    Science Advisor
    Gold Member

    You mean, why does the expression:
    $$\frac{1}{24}(x^2-1)$$
    not return an integer when ##x## is an odd multiple of 3? Think about what "odd multiple of 3" means mathematically and substitute that for ##x## in the expression above to see what you get.
     
  8. Dec 20, 2016 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Can x2-1 be divisible by 3 if x is divisible by 3?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: A question regarding multiples of 3
Loading...