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

1. ## 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

2. Originally Posted by JBroeng
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

3. Originally Posted by JBroeng
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.

4. Yes A, D, H, r, M, P is constants and F(r) is a function.

5. 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

6. 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 $\frac{A}{2}$.

7. Thank you so much !!!

8. 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

9. 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...