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## Homework Statement

At what distance along the central axis of a ring of radius R = 0.200 m and uniform charge is the magnitude of the electric field due to the ring's charge maximum? What is the positive solution for z?

## Homework Equations

E = [itex]\frac{kqz}{(z^2+R^2)^(3/2)}[/itex]

## The Attempt at a Solution

I know I should differentiate that above equation with respect to z and then set it equal to 0 to get z but i just dont know how to differentiate that ..

E = [itex]\frac{kqz}{(z^2+R^2)^(3/2)}[/itex]

the k and the q are held as constants and can be taken out of the differentiation ..

= kq*[[itex]\frac{d}{dz}[/itex]((z

^{2}+R

^{2})

^{3/2}]

isn't [itex]\frac{d}{dz}[/itex]((z

^{2}+R

^{2})

^{3/2}= -3z(z

^{2}+R

^{2})^(-5/2) ??

so it would be kq [-3z(z

^{2}+R

^{2})^(-5/2)]

but that doesn't work for when you set it = 0. what am i supposed to be doing that im not