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Math Help - Solve for the specified variable?

  1. #1
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    Solve for the specified variable?

    What do I do, I'm the HORRIBLE when it comes to math :'( I have a lot more of these but i need to learn how to do this.

    1/a + 1/b = c for a



    P= A/1+rt for r


    I= kE/R for R
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  2. #2
    Super Member Quacky's Avatar
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    \frac{1}{a}+\frac{1}{b}=c

    Start by removing the fractions (just multiply through by the denominators, as below):

    a(\frac{1}{a}+\frac{1}{b})=a\times c

    1+\frac{a}{b}=ac

    b(1+\frac{a}{b})=ac\times b

    b+a=abc

    Rearrange so that all terms involving 'a' are on one side of the equation:

    b=abc-a

    Factor out an a:

    b=a(bc-1)

    Divide through by the non-a factor:

    \frac{b}{bc-1}=a

    Try the others yourself, it's the same principle! Post your working if you're still unable to continue.
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  3. #3
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    Quote Originally Posted by mrmyers22 View Post
    1/a + 1/b = c for a
    Multiply each term by ab:
    b + a = abc
    Get the terms with "a" together:
    abc - a = b
    factor left side:
    a(bc - 1) = b
    divide each side by (bc - 1):
    a = b / (bc - 1)
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