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Ab+ac/a=b+ac Equality

  1. Jan 26, 2010 #1
    1. The problem statement, all variables and given/known data



    So i get a home work problem that goes like this. ab+ac/a=b+ac.

    is the left side of the equation not equal to or equal to the right side?
     
  2. jcsd
  3. Jan 26, 2010 #2

    Borek

    User Avatar

    Staff: Mentor

    Re: Equality

    [tex]ab + \frac {ac} {a} = b + ac[/tex]

    or

    [tex]\frac {ab + ac} {a} = b + ac[/tex]

    ?
     
  4. Jan 26, 2010 #3
    Re: Equality

    thanks Borek. My answers in the back of my textbook say it is not equal but i can't figure out why. ill ask my teacher tommorow i just wanted to get some help ahead of time. thanks
     
  5. Jan 26, 2010 #4

    Mark44

    Staff: Mentor

    Re: Equality

    Please read what Borek wrote. He's not giving you and answer; he's trying to understand what you meant. Please use parentheses to indicate which expressions are in the numerator on the left side.
     
  6. Jan 26, 2010 #5
    Re: Equality

    either way they arent equal. so what does it matter
     
  7. Jan 26, 2010 #6

    Mark44

    Staff: Mentor

    Re: Equality

    It's always better to know exactly what the problem is than to not know, that's why it matters.
     
  8. Jan 26, 2010 #7
    Re: Equality

    But it doesn't matter with respect to his answer. Neither of them are equal. If the problem represented something physical then i understand that.'

    And for the record, you support your statements poorly. Why should i know this? oh because its better to know then not to know?
     
  9. Jan 26, 2010 #8

    Char. Limit

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    Gold Member

    Re: Equality

    Well, the second equation is equal when a=1...

    And the first equation is equal when a=1 and b=c.

    They aren't necessarily unequal.
     
  10. Jan 26, 2010 #9

    Mark44

    Staff: Mentor

    Re: Equality

    Yes, that is true. On the other hand, a large number of posters in this forum present problems that are ambiguous. For my part, I would rather make these posters aware that their problems can be interpreted in multiple ways than work all possible variants of these problems.
    I don't see how that makes a difference.
    So are you saying that it is not better to know exactly what the problem is?
     
  11. Jan 26, 2010 #10
    Re: Equality

    Ok I looked at it again and I do realize he was just asking which form of the problem I meant and the second one is the correct one. I still do not understand why they are unequal.
     
  12. Jan 26, 2010 #11

    Mark44

    Staff: Mentor

    Re: Equality

    [tex]\frac {ab + ac} {a} = \frac{a(b + c)}{a} = b + c \neq b + ac[/tex]
    The first and last expressions above are not identically equal. They are conditionally equal for some values of the variables, such as a = 1.
     
  13. Jan 26, 2010 #12
    Re: Equality

    Cornraker, just because they are equal for some values does not in a sense warrant that equal sign.
     
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