Derivative of quotient with same variables on top and bottom

[bill nye scienceguy!]

Homework Statement

a=g.[(M-m)/(M+m)]

how do i go about finding the partial derivative wrt m?

Homework Equations

The Attempt at a Solution

i started by rearranging it to the form a=g.(M-m)(M+m)^-1, i used the chain rule to find the derivative of (M+m)^-1 to be -(M+m)^-2 but I'm not sure where to go from there or even if that was the right approach to take. any help?

thanks

 

[HallsofIvy]

I don't see why you would have a problem with this. Would you be able to find the derivative, with respect to x, of (x- m)/(x+ m) if m were a constant? What about (M-x)/(M+ x) if M is a constant? It's exactly the same thing.

You can write (M-m)(M+m)^-1 and use the chain rule together with the product rule or you can keep it as (M-m)/(M+m) and use the quotient rule.