Results 1 to 3 of 3

Math Help - Disprove a statement

  1. #1
    Member
    Joined
    Jan 2009
    From
    Kingston, PA
    Posts
    96

    Disprove a statement

    Hey everyone,
    Im being asked to disprove: If X and Y are positive real numbers, then the SqRt( X+Y) = SqRt(X) + SqRt(Y). As a counterexample, would letting x= 25 and Y=9 be acceptable? Since SqRt(x+y) would equal SqRt(34) and SqRt(X) + SqRt(Y)= 5+3=8 and there not equal?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Smile

    Quote Originally Posted by nikie1o2 View Post
    Hey everyone,
    Im being asked to disprove: If X and Y are positive real numbers, then the SqRt( X+Y) = SqRt(X) + SqRt(Y). As a counterexample, would letting x= 25 and Y=9 be acceptable? Since SqRt(x+y) would equal SqRt(34) and SqRt(X) + SqRt(Y)= 5+3=8 and there not equal?
    Yes, this will work.

    If you want an even simpler counterexample, consider X=Y=1.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2009
    Posts
    11
    The more algebraic proof would be to square both sides of the equation and show them they are not the same.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trying to prove or disprove statement about irreducibility
    Posted in the Advanced Algebra Forum
    Replies: 0
    Last Post: January 16th 2012, 01:10 PM
  2. Prove or Disprove the Following:
    Posted in the Discrete Math Forum
    Replies: 3
    Last Post: September 8th 2010, 05:35 AM
  3. Prove or disprove
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: November 2nd 2009, 03:30 PM
  4. prove or disprove
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: October 25th 2008, 07:41 AM
  5. Disprove a statement
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 16th 2007, 08:30 AM

Search Tags


/mathhelpforum @mathhelpforum