algebra precalculus - Why is the quadratic equation $ax^2+bx+c=0$?

Shouldn't it be $y=ax^2+bx+c$? According to Wikipedia, it is $ax^2+bx+c=0$.

I guess that they are both equations, right?

Answer

They are both equations that involve quadratics, but the usual meaning of "quadratic equation" is that it has only one variable, while $y=ax^2+bx+c$ has two variables ($x$ and $y$).