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Algebra, rearranging equations

  1. Nov 3, 2009 #1
    Hi hope someone can help explain this for me.

    If i have the equation of a=square root of b/b+1 why do can i not cancel the b's? If the equation was square root of bc/bd i can cancel the b's right?

    Thanks
    James
     
  2. jcsd
  3. Nov 3, 2009 #2

    Mark44

    Staff: Mentor

    You can cancel the b's only when they are factors of both the numerator and denominator. b is not a factor of the expression b + 1. Put some numbers in and see how it works. If b = 3, then your expression is 3/(3 + 1) = 3/4. If you (mistakenly) cancelled b, you would get 1/(1 + 1) = 1/2, which is, of course, incorrect.

    In your second example, b is a factor of both numerator and denominator, so you can cancel to get c/d.
     
  4. Nov 3, 2009 #3
    Ok Mark thanks for your reply.

    James
     
  5. Nov 3, 2009 #4

    symbolipoint

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    When someone presents a question like this, the trouble is ignoring of the properties of numbers which the person is expected to learn and use.

    What is the justification for either canceling the b's of not canceling the b's?
     
  6. Nov 4, 2009 #5

    arildno

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    To follow up symbolipoint's post:

    OP's expression, "a=square root of b/b+1" is extremely ambiguous:

    Which interpretation to choose:
    1. [tex]a=\sqrt{\frac{b}{b}+1}[/tex] "a=square root of ((b/b)+1)"

    2. [tex]a=\sqrt{\frac{b}{b+1}[/tex] "a=square root of (b/(b+1))"

    3. [tex]a=\frac{\sqrt{b}}{b}+1[/tex] "a=((square root of b)/b)+1)"

    4. [tex]a=\frac{\sqrt{b}}{b+1}[/tex] "a=(square root of b)/(b+1)"

    5. [tex]a=\sqrt{\frac{b}{b}}+1[/tex] "a=(square root of (b/b))+1"
     
    Last edited: Nov 4, 2009
  7. Nov 4, 2009 #6
    Thanks for the reply's it was statement 2 that I was considering in the problem.
     
  8. Nov 4, 2009 #7
    Hi you seem to know LaTeX.

    I know this forum supports LaTeX and it's nice, but i want learn LaTeX, so what is your best advice, i.e. what LaTeX programs are good for writing Lab-reports?

    another question i've got is, do you write the code for every expression or do you use the forum help with inserting code from menu?
    Which one would you recommend?
    thanks
     
  9. Nov 5, 2009 #8

    arildno

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    But, do you understand how unclear your question was?
     
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