the answer
y=−x^2−2x-24 is like the form of y=ax² +bx +c, to find the vertex we use the formula:
the x intercept according to the vertex is x=-b/2a, and the vertex V is a point such that V [-b/2a, f(-b/2a)]
the x intercept is x= -(-2) / 2(-1) =-1, and f(-1)= -1 +2 -24= -23
the vertex is V(-1, -23)