y'(x)=-\frac{2 a}{128 a^4 x^3-96 a^3 x^2 y(x)^2-32 a^3 x^2+24 a^2 x y(x)^4+16 a^2 x y(x)^2-2 a y(x)^6-2 a y(x)^4-2 a-y(x)}