Giải các hệ phương trình sau:
a) $\left\{\begin{matrix} 1+x^{3}y^{3}=19x^{3} & & \\ y+xy^{2}+6x^{2}=0 & & \end{matrix}\right.$
b) $\left\{\begin{matrix} 2y^{3}+3xy^{2}=8 & & \\ x^{3}y-2y=6 & & \end{matrix}\right.$
c) $\left\{\begin{matrix} 27x^{3}y^{3}-9y^{3}+125=0 & & \\ 45x^{2}y-6y^{2}+75x=0 & & \end{matrix}\right.$
d) $\left\{\begin{matrix} x^{3}+4y=y^{3}+16x& & \\ 1+y^{2}=5(1+x^{2}) & & \end{matrix}\right.$
e) $\left\{\begin{matrix} x^{2}+8y^{2}=12 & & \\ x^{3}+2xy^{2}+12y=0 & & \end{matrix}\right.$
f) $\left\{\begin{matrix} x^{3}+y^{3}=xy^{2}+1 & & \\ 4x^{4}+y^{4}=4x+y & & \end{matrix}\right.$