Question

求方程x^3y-xy^3+2x^2+2y^2+4=0的解

Answer 1

xy(x+y)(x-y)+2(x^2+y^2)+4=0

[y(x+y)+2] [x(x-y)+2]=0

因此

有y(x+y)+2=0,得：x=-2/y-y

或x(x-y)+2=0,得：y=x+2/x