what values of c is the locus of the function (x^2+x+y+3)y+z(x+y+3)+c a surface?
ok so my f=yx^2+yx+y^2+3y+zx+zy+3z+c..
i know that on a surface df cant equal zero.. and
{x,y,z in R^3 : f(x,y,z)=0}
df=(2xy+y+z)dx+(x^2+x+2y+z+3)dy+(x+y+3)dz
2xy+y+z=0
x^2+x+2y+z+3=0
x+y+3=0
im confused now.. am i meant to solve them? coz i get very bad answers