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Math Help - Simplify expression, isolating Q

  1. #1
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    Simplify expression, isolating Q


    Thank you i advance :-)
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  2. #2
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    Re: Simplify expression, isolating Q

    Hey mrtn.

    Hint: Take the -dS/Q^2 term to the RHS side and then take the reciprocal of both sides which will give Q^2/dS = blah. After this you multiply both sides by dS and take the square root.

    Show us your attempts so we can guide you through them.
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  3. #3
    Member agentmulder's Avatar
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    Re: Simplify expression, isolating Q

    Quote Originally Posted by mrtn View Post

    Thank you i advance :-)
    Question: What is the subscript on h for?

    I would move the fraction with Q^2 to the right hand side of the equation to start.

     \frac{h}{2} - \frac{dh}{2p} = \frac{ dS}{Q^2}

    Combine fractions on the left

     \frac{h(p - d)}{2p} = \frac{dS}{Q^2}

    Divide both terms in the parenthesis by p

     \frac{h(1 - \frac{d}{p})}{2} = \frac{Q^2}{dS}

    Invert both sides

     \frac{2}{h(1 - \frac{d}{p})} = \frac{Q^2}{dS}

    Multiply by dS

     \frac{2Sd}{h(1 - \frac{d}{p})} = Q^2

    Extract the root

     Q = \pm \sqrt{\frac{2Sd}{h(1 - \frac{d}{p})}}

    Question: What is the subscript on h for?

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  4. #4
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    Re: Simplify expression, isolating Q

    Hey chiro.

    Thank you for your hints.

    This is what I can come up with:



    I still cant get there.

    Sorry about the h / hl thing - they are the same
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  5. #5
    Member agentmulder's Avatar
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    Re: Simplify expression, isolating Q

    Quote Originally Posted by mrtn View Post
    Hey chiro.

    Thank you for your hints.

    This is what I can come up with:



    I still cant get there.

    Sorry about the h / hl thing - they are the same
    You cannot invert before you combine because it doesn't work COMBINE FIRST , then invert.

     2 + 3 = 5 but  \frac{1}{2} + \frac{1}{3} \ne \frac{1}{5}

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