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Math Help - algebra problems

  1. #1
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    Exclamation algebra problems with fractions and letters

    please help me with these algebra problems! thank you!

    1.) solve
    b-4ac
    x=
    2a
    for "a"



    2.)simplify:
    (5y)/(4xy2)(3)/(5x)(-3x2y)/(3xy)

    * the / means its a fraction.
    Last edited by kawaiiway; August 21st 2012 at 11:32 PM.
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  2. #2
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    Re: algebra problems

    1) x=\frac{b-4ac}{2a}\,\, multiply both sides by 2a

    so you get (2a)x=(\frac{b-4ac}{2a})*2a\,\, so the 2a's cancel each other

    2ax=b-4ac add 4ac to both sides

    2ax+4ac=b-4ac+4ac in LHS take (a) as common factor

    a(2x+4c)=b divid both sides by the term (2x+4c)

    \frac{a(2x+4c)}{2x+4c}=\frac{b}{2x+4c}


    a=\frac{b}{2x+4c}
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  3. #3
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    Re: algebra problems

    1st one: easier if you use criss-cross multiplication (example: if a/b = c/d, then ad = bc):
    2ax = b - 4ac : 2ax + 4ac = b : a(2x + 4c) = b : a = b / (2x + 4c)

    2nd one: start by cancelling where possible; like 5y / (4xy^2) = 5 / (4xy)
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  4. #4
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    Re: algebra problems with fractions and letters

    wow! thank you so much! i understand!!(^∇^)
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  5. #5
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    Re: algebra problems

    thank you!!! i understand! thank you for helping with both problems ><
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