Friday, May 18, 2007

ALGEBRA QUESTION OF THE DAY

If x and y are prime numbers such that x > y > 2, then x^2 − y^2 must be divisible by which one of the
following numbers?
(A) 3
(B) 4
(C) 5
(D) 9
(E) 12
at

8 comments:

  1. AnonymousMay 18, 2007 at 1:13 PM

    B

    ReplyDelete
  2. UnknownMay 20, 2007 at 8:46 PM

    b

    ReplyDelete
  3. UnknownMay 21, 2007 at 10:38 PM

    B

    ReplyDelete
  4. AnonymousMay 22, 2007 at 10:30 AM

    explain

    ReplyDelete
  5. AnonymousMay 22, 2007 at 10:31 AM

    for ex...5>3>2...thn B is correct
    Bt if 4>3>2...thn...16-9=7 !!!
    thn wats the ans here....?

    ReplyDelete
  6. AnonymousMay 23, 2007 at 7:53 AM

    can some1 explain?

    ReplyDelete
  7. Aditya`s takeMay 23, 2007 at 11:27 PM

    the question says prime no.

    so we take 2 prime nos..

    for eg 5 and 3.....5*5-3*3=16 divisible by 4

    aand if we take 7*7-3*3 =40 its again divisible by 4.....so the answer is ...b

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  8. Vishal NaiduMay 31, 2007 at 6:41 AM

    Let X and Y be the primes......

    since both X & Y are !=2

    X & Y are both odd numbers...
    trivial evens can't be primes....
    so let X = 2m+1
    Y = 2n+1

    => X^2 - Y^2 = (X+Y) (X-Y)
    = (2m+2n+2)(2m-2n)
    = 4 (m+n+1)(m-n)

    so definitely divisible by 4 :)

    ReplyDelete