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Math Help - Multiplying Rational Expressions

  1. #1
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    Multiplying Rational Expressions

    3x+6
    _______ *
    X^2-4

    x^2-2x
    ________
    9

    *the x^2 cancel our right?
    *do I factor 3x + 6 into 3(x+2)?
    Can someonw please walk me through this?
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  2. #2
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    Quote Originally Posted by spikeymikey View Post
    3x+6
    _______ *
    X^2-4

    x^2-2x
    ________
    9

    *the x^2 cancel our right?
    *do I factor 3x + 6 into 3(x+2)?
    Can someonw please walk me through this?
    We need to factor before we reduce

    \frac{3x+6}{x^2-4} \cdot \frac{x^2-2x}{9} \iff \frac{3(x+2)}{(x-2)(x+2)} \cdot \frac{x(x-2)}{9}

    reducing the above we get

    \frac{3(x+2)}{(x-2)(x+2)} \cdot \frac{x(x-2)}{9}=\frac{x}{3}
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  3. #3
    MHF Contributor Mathstud28's Avatar
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    Ok

    Quote Originally Posted by spikeymikey View Post
    3x+6
    _______ *
    X^2-4

    x^2-2x
    ________
    9

    *the x^2 cancel our right?
    *do I factor 3x + 6 into 3(x+2)?
    Can someonw please walk me through this?
    IF the first problem is supposed to be \frac{3x+6}{x^2-4}...then you do the following...factor top and bottom to get \frac{3(x+2)}{(x+2)(x-2)}...cancel the x+2 to get \frac{3}{x-2}
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  4. #4
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    Quote Originally Posted by TheEmptySet View Post
    We need to factor before we reduce

    \frac{3x+6}{x^2-4} \cdot \frac{x^2-2x}{9} \iff \frac{3(x+2)}{(x-2)(x+2)} \cdot \frac{x(x-2)}{9}

    reducing the above we get

    \frac{3(x+2)}{(x-2)(x+2)} \cdot \frac{x(x-2)}{9}=\frac{x}{3}
    Thank you
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  5. #5
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    So for....
    x^2+6x+5 over 3x^2+3x Mutiplied by x^2-x-20 over x^2-25

    I got a final result of 1 over 3x.....is that correct?
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  6. #6
    Behold, the power of SARDINES!
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    Red face sorry :(

    Quote Originally Posted by spikeymikey View Post
    So for....
    x^2+6x+5 over 3x^2+3x Mutiplied by x^2-x-20 over x^2-25

    I got a final result of 1 over 3x.....is that correct?
    \frac{x^2+6x+5}{3x^2+3x} \cdot \frac{x^2-x-20}{x^2-25} \iff \frac{(x+1)(x+5)}{3x(x+1)} \cdot \frac{(x-5)(x+4)}{(x-5)(x+5)}= \frac{(x+4)}{3x}
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  7. #7
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    Quote Originally Posted by TheEmptySet View Post
    \frac{x^2+6x+5}{3x^2+3x} \cdot \frac{x^2-x-20}{x^2-25} \iff \frac{(x+1)(x+5)}{3x(x+1)} \cdot \frac{(x-5)(x+4)}{(x-5)(x+5)}= \frac{(x+4)}{3x}
    ok I see where I made the mistake
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  8. #8
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    I need help with one more....

    7x^3*y^4 over 6xy DIVIDED by 14x^2*y^2 over 36x^2y
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  9. #9
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    Quote Originally Posted by spikeymikey View Post
    I need help with one more....

    7x^3*y^4 over 6xy DIVIDED by 14x^2*y^2 over 36x^2y
    Do yourself and do us a favor and start a new thread if you have a new problem to solve.

    Your problem was answered here: http://www.mathhelpforum.com/math-he...949-post1.html
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