Math Question, hard

This is a discussion on Math Question, hard within the A Brief History of Cprogramming.com forums, part of the Community Boards category; There is a question that I can never figure out why it is wrong. Here is the question: 16-36=25-45 = ...

  1. #1
    A Banana Yoshi's Avatar
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    Math Question, hard

    There is a question that I can never figure out why it is wrong. Here is the question:

    16-36=25-45
    = -20
    16-36+20.25=25-45+20.25
    add 20.25 to both sides

    FOIL / Complete the square...
    (4-(9/2))^2 = (5-(9/2))^2
    Sqrt it.
    4-(9/2) = 5-(9/2)
    add both sides by 9/2
    4=5

    why is it wrong?
    This question held me prisoner for 5 hours and I just lost my last bit of hand-eye coordination.
    ---------------------------
    Engineer223
    Last edited by Yoshi; 12-02-2001 at 11:42 PM.
    Yoshi

  2. #2
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    well, I'll take a look at it, but I'm sure that the problem is with the sqrt.

    you see, you can't do

    a^2=b
    a=sqrt(b)

    that's not true, the solution is

    a^2=b
    a=(+/-)sqrt(b)

    that's because 5^2=(-5)^2=25

    but I'll give you the full answer in a while

    Oskilian

  3. #3
    Linguistic Engineer... doubleanti's Avatar
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    the trick is that when you square it, it can remove the negative... when you square it you are supposed to take the negative on the four and the positive on the five, thus giving you the difference... [+-0.5]
    hasafraggin shizigishin oppashigger...

  4. #4
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    yup, that's it

    Oskilian

  5. #5
    Linguistic Engineer... doubleanti's Avatar
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    hasafraggin 3 minutes...
    hasafraggin shizigishin oppashigger...

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    What are you studying? I mean what grade.

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    kindergarten.

    j/k

  8. #8
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    LOL, but don't be rude

  9. #9
    Back! ^.^ *Michelle*'s Avatar
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    Haha, I got the a similar problem once...

    y=root X (can't type the root sign)
    is a function

    y^2=X
    (square both sides)
    is not a function...
    Michelle (o^.^o)
    *Unique*
    Kaomoji House

  10. #10
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    y^2=X is a function.

  11. #11
    A Banana Yoshi's Avatar
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    Another Question

    What is the answer to (10˛ + 11˛ + 12˛ + 13˛ + 14˛) / 365 WITHOUT using your calculator.

    Hint: {}
    --------------------------
    Engineer223

    Midterm on Friday!!! ahhhh!!! [banging my head on the wall]
    Yoshi

  12. #12
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    simple...2 :-)
    and no I didnt use a calculator.

  13. #13
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    Originally posted by Gades
    y^2=X is a function.
    no it isn´t, a function must have only one X value for each Y value, and this one doesn´t (for example: if X=4, y can be 2 or -2)

    Oskilian

  14. #14
    & the hat of GPL slaying Thantos's Avatar
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    Ok here is one for you all.

    y^x = x^y

    x and y are not equal.

  15. #15
    A Banana Yoshi's Avatar
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    x=4
    y=2
    --
    Yoshi

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