Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I really do not get proofs AT ALL.

  1. Jul 12, 2010 #1
    I really do not get proofs AT ALL. Stuff like this....

    "Prove that (n+1)2 [tex]\geq[/tex]3n if n is a positive integer with n[tex]\leq[/tex]4."

    Proof by exhaustion would be applied here.. what the book tells me.




    "Show that there are no solutions in integers x and y of x2+3y2=8."

    Then there's also "Constructive Existence Proof" and "Nonconstructive proof". No idea how to do any one of them. How do I approach those equations, and how do I know which proof I need to use??
     
    Last edited by a moderator: Jul 12, 2010
  2. jcsd
  3. Jul 12, 2010 #2

    EnumaElish

    User Avatar
    Science Advisor
    Homework Helper

  4. Jul 12, 2010 #3

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: proofs

    I've edited out some whining and language. :grumpy:
     
  5. Jul 12, 2010 #4

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: proofs

    Something is a (formal) proof if and only if it adheres to a certain set of directions. (the rules of logic)

    There is a wide variety of proofs, because the rules of logic allow many different possibilities at each step of the proof.

    The "game" of proving things is to find a proof that starts with a useful hypothesis and ends with a useful conclusion. (And in this problem, you're told what the hypothesis and the conclusion are)



    Now, what do the rules of logic say a "proof by exhaustion" is?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook