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Math Help - Is there anyone who can differentiate this function, and then isolate the Q?

  1. #1
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    Is there anyone who can differentiate this function, and then isolate the Q?

    Hi

    Can anyone help me differentiate this function with respect to Q, and then isolate the Q?

    J(Q,r) = ((A*D)/Q) + H((Q/2) + r + M) + ((P*F(r)*D)/Q)

    Thank you

    JBroeng
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  2. #2
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    Quote Originally Posted by JBroeng View Post
    Hi

    Can anyone help me differentiate this function with respect to Q, and then isolate the Q?

    J(Q,r) = ((A*D)/Q) + H((Q/2) + r + M) + ((P*F(r)*D)/Q)

    Thank you

    JBroeng
    Is H a constant or a function?

    CB
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  3. #3
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    Quote Originally Posted by JBroeng View Post
    Hi

    Can anyone help me differentiate this function with respect to Q, and then isolate the Q?

    J(Q,r) = ((A*D)/Q) + H((Q/2) + r + M) + ((P*F(r)*D)/Q)

    Thank you

    JBroeng
    Assuming H is a constant this is
    J(Q,r)= AD Q^{-1}+ HQ/2+ Hr+ HM+ PF(r)DQ^{-1}
    and can be easily differentiated using the power rule.
    Last edited by HallsofIvy; May 27th 2010 at 02:53 AM.
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  4. #4
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    Yes A, D, H, r, M, P is constants and F(r) is a function.
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  5. #5
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    Hi again

    I know it might be a dum question but how do I differentiate (H*Q)/2?

    I have totally forgotten how to differentiate a fraction.

    JBroeng
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  6. #6
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    The derivative of Ax is A. (That's a linear function so the derivative is just the slope.)

    The fact that A is a fraction is irrelevant: the derivative of \frac{A}{2}Q with respect to Q is \frac{A}{2}.
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  7. #7
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    Thank you so much !!!
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  8. #8
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    Sorry but bother you again ...but can any of you see how they get from a to b?

    a) Q^2 = (2(A+P*f(r))D)/H

    b) Q = (P*D*f(r))/H

    Thank you for helping me...

    JBroeng
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  9. #9
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    I have found the solution.....they differentiate the function with respect to Q and r , and isolate Q in both of those function.....Thank you for all your help...
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