[math]8r^2\left[\left(1-d^2\right)^2-r^2\left(1+d^2\right)\right][/math][math]\left(\left(1+d^2\right)\left[\left(1-d^2\right)^4+4r^4d^21\right]-8r^2d^2\left(1-d^2\right)^2\right)[/math][math]=\left[\left(1-d^2\right)^4-4r^4d^2\right]^2[/math]