1. Consider the electric dipole on the x-axis where a positive charge q is at (a,0) and a negative charge -q is at (-a,0) such that the distance between the two charges is 2a. Show that the electric field at a distant point on the +x axis is E(x)= 4kqa/x^3. 2. Relevant equations: E=kq1q2/r^2 3. The attempt at a solution: E=kq/x^2 - kq/(x+2a)^2 E(simplified)=kq[x^-2 - (x^2+4a)^-1] E=4kqa/(x^4+4x^2a) This clearly gives me the wrong solution, but I know it works when I switch my r values. Why is it that I have to use x-a and x+a for r instead of x and x-2a? Why does shifting the y-axis change the answer since x>>2a, it shouldn't matter, but I'm getting a different solution using this approach. Please help me understand this problem! Thanks!