a circular ring of wire radius r lies in a plane perpendicular to the x-axis and is centered at the origin. The ring has a positive electric charge spread uniformly over it. The electric field in the x-direction, E, at the point x on the x-axis is given by E= kx/(x^2 + r^2)^(3/2) for k>0. At what point on the x-axis is the field greatest? Least? After taking the first derivative i ended up with: E' = k(-2x^2 + r^2 - 3xr)/(x^2 + r^2)^(5/2) i know after the derivative im supposed to find the critical points then classify them and find the global min and global max, but for critical points i end up with only a zero, waht does it look like is wrong here?