I'm just starting to learn about conic sections, and it says in my text that their general equation is .
Is that an error? Isn't it supposed to be not just ?
Thanks for your help.
Actually, now that I think about it, if there is an xy term then the conic is rotated by some angle. You stated that you're starting to learn about conic sections, so the book probably omitted the xy term deliberately. This means that in parabolas & hyperbolas, without the xy term, the curves will only open upward/downward/left/right. And in ellipses, the major/minor axes will only be horizontal/vertical lines.