# Thread: Rate of change of power

1. ## Rate of change of power

I used an image because I already had the format done:

2. Are you familiar with the differential calculus? You need to look up the "Quotient Rule".

Also, the notation is lacking. "130/" is no good.

3. I've learned the quotient rule.
I don't understand what you mean by that :S

I've tried solving the problem by using the quotient rule but I ended up with a very different answer than from the back.

4. $P = \frac{130R}{(R+0.8)^2}$

$\frac{dP}{dR} = \frac{(R+0.8)^2 \cdot 130 - 130R \cdot 2(R+0.8)}{(R+0.8)^4}$

$\frac{dP}{dR} = \frac{130(R+0.8)[(R+0.8)-2R]}{(R+0.8)^4}$

$\frac{dP}{dR} = \frac{130(0.8-R)}{(R+0.8)^3}$

5. Thanks - I did it again and it worked. I derived in wrong in the first place.
Thanks.