I wouldn't use the phrase "extends from." If the leading coeff. is neg, then the graph opens downward. Without more info we do not know the max of this fn. If we did know it, we could state that the graph max is (value) and that the graph "extends downward from this value."
I'm not sure what you mean by "extends from", but a negative leading coefficient of a quadratic causes it to become concave, as in extending downwards. For y = -x^2, the function's maximum is 0.
