The general equation of conics of the form: $$ Ax^2+Bxy+Cy^2+Dx+Ey+F=0 $$
and it is said that for a parabola $A=0$ or $C=0$ or $AC=0$ and $Bxy$ is associated with the rotations.
But for the given conic, $16x^2+8xy+y^2-74x-78y+212=0$
It seems to be a parabola even though $A=16\neq0$ and $B=1\neq0$.
What am I missing here in the general form of conics ?
What about the case with other conics ?
$A\neq C$ and $AC>0$ for ellipse
$A\neq C$ and $AC<0$ for hyperbola, etc.