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Homework Help: Multiplying Rational Expressions

  1. Apr 2, 2006 #1
    This is a question I have to do for tomorrow

    [tex]\frac{1+4x+4x^2}{x}\times\frac{3x^4}{12x^2-3}[/tex].

    I just factor the tops and then cancel where I can. This is what I came up with:

    [tex]\frac{3x^4}{12x^3-3x}[/tex]

    But the answer key says:

    [tex]\frac{x^3(1+2x)}{2x-1}[/tex]

    What have I done wrong?
     
  2. jcsd
  3. Apr 2, 2006 #2
    You aren't factoring carefully enough. You've got leftover factors floating around. Write out ALL of the steps!

    [tex]\frac{1+4x+4x^2}{x}\times\frac{3x^4}{12x^2-3}[/tex]

    [tex]=\frac{(2x+1)(2x+1)}{x} \times \frac{3x^4}{3(2x-1)(2x+1)}[/tex]

    NOW do your cancelling.

    -Dan
     
  4. Apr 2, 2006 #3
    Ouch. That hurt my pride. I forget to factor the factor usually, that's going to kill me one day.

    thanks for pointing out that pesky little mistake.
     
  5. Apr 3, 2006 #4
    Happens to the best of us. No worries, mate! :biggrin:

    -Dan
     
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