Answer
(a) See graph, opens down, vertex $(-3,9)$, axis of symmetry $x=-3$, intercept(s) $(0,0),(-6,0)$.
(b) domain $(-\infty,\infty)$, range $(-\infty,9]$.
(c) decreasing on $(-3,\infty)$, increasing on $(-\infty,-3)$.
Work Step by Step
(a) See graph for $y=-x^2-6x=-(x+3)^2+9$, we can find that the graph opens down, vertex $(-3,9)$, axis of symmetry $x=-3$, y-intercept $(0,0)$, x-intercept(s) $(0,0),(-6,0)$.
(b) We can determine the domain $(-\infty,\infty)$, range $(-\infty,9]$.
(c) The function is decreasing on $(-3,\infty)$, increasing on $(-\infty,-3)$.
