p = [E^(2) R]/(r + R)^2

I began by multiplying both sides by (r +R)^2.

I then got this:

p(r + R)^2 = E^(2) R

I then simplified the left side and got this:

pr^2 + 2rR + R^2 = E^2 R

I subtracted pr^2 from both sides and got this:

2rR + R^2 = E^2 R - pr^2

I then subtracted both sides by E^2 R.

2rR + R^2 - E^2 R = -pr^2

I then factored out the upper case letter R on the left side and got this:

R(2r + R - E^2) = -pr^2

This is where I got stuck.

Notice that there is another upper case letter R inside the parentheses.

Where do I go from there?