Answer
(a) See graph, opens up, vertex $(-1,-9)$, axis of symmetry $x=-1$, y-intercept $(0,-8)$, x-intercept(s) $(2,0),(-4,0)$.
(b) domain $(-\infty,\infty)$, range $[-9,\infty)$.
(c) increasing on $(-1,\infty)$, decreasing on $(-\infty,-1)$.
Work Step by Step
(a) See graph for $y=x^2+2x-8=(x+1)^2-9$, we can find that the graph opens up, vertex $(-1,-9$, axis of symmetry $x=-1$, y-intercept $(0,-8)$, x-intercept(s) $(2,0),(-4,0)$.
(b) We can determine the domain $(-\infty,\infty)$, range $[-9,\infty)$.
(c) The function is increasing on $(-1,\infty)$, decreasing on $(-\infty,-1)$.
