// 2 \\ || x || ||----------|| || 2 || |\x + 9*x*y/| |------------| \ x / -------------- 2 2 x - 81*y
x/((x^2 - 81.0*y^2)*(x^2 + 9.0*x*y))
x ------------------------- / 2 2\ / 2 \ \x - 81*y /*\x + 9*x*y/
x ------------------------- / 2 \ / 2 2\ \x + 9*x*y/*\x - 81*y /