Results 1 to 8 of 8

Math Help - 1 = 2

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    2

    1 = 2

    I know there is error in this but! If i can substitute 1 for x here.


    Quote Originally Posted by http://www.amatecon.com/1equals2errors.html

    x = 1 set x equal to 1
    x2 = x multiply both sides by x
    x2 - 1 = x - 1 subtract 1 from both sides
    (x - 1)(x + 1) = x - 1 separate left side into factors
    x + 1 = 1 divide both sides by (x - 1)
    1 + 1 = 1 substitute 1 for x
    2 = 1
    Quote Originally Posted by Error

    Division by (x-1) is not allowed since x=1 and therefor x-1=0 and division by zero is an undefined operation.
    Why can't I substitute 1 for x in this problem.

    Substitute 1 for x.

    1+1=x

    2=1 ! omg.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member Greengoblin's Avatar
    Joined
    Feb 2008
    From
    UK
    Posts
    182
    I'd say you've answered your own question:

    Division by (x-1) is not allowed since x=1 and therefor x-1=0 and division by zero is an undefined operation.
    Division by zero leads to bogus proofs like this.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2008
    From
    Beijing, China
    Posts
    17
    the correct mathematical notation is:
    limit as x tends to 1 for (x^2-1)/(x-1)
    this limit is equal to 2 and you cannot just get (x-1) out of the limit and multiply it by to on the RHS.
    God Bless
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member Greengoblin's Avatar
    Joined
    Feb 2008
    From
    UK
    Posts
    182
    The point is, he's let \frac{0}{0}=1 when actually it's indeterminate.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Dec 2008
    Posts
    2
    0/0 is 0

    Plain and simple.

    but
    x-1=k-1
    if x = 2 and k = 3

    2-1=3-1
    1=2

    NVM x-1=k-1 would not be true !!! sorry I'm stoooopid.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member Greengoblin's Avatar
    Joined
    Feb 2008
    From
    UK
    Posts
    182
    Yep, all you can say about x-1=k-1 is x=k, and nope, \frac{0}{0}\ne0, it is simply not defined.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    Quote Originally Posted by Error View Post
    0/0 is 0

    Plain and simple.

    but
    x-1=k-1
    if x = 2 and k = 3

    2-1=3-1
    1=2

    NVM x-1=k-1 would not be true !!! sorry I'm stoooopid.
    Let me just say that a thread which goes against the basic principles of maths (like 1+1=2 and 0/0 = 0) is bound to be closed and deleted. Plus it does everything but earn you respect.
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Error View Post
    0/0 is 0

    Plain and simple.
    If you are serious with this you need to go back to school and repeat elementary arithmetic.

    CB
    Follow Math Help Forum on Facebook and Google+


/mathhelpforum @mathhelpforum