a.
From the graph we notice that when x=-1 the value of the function is zero; therefore:
[tex]f(-1)=0[/tex]
and it is not negative.
b.
The function is positive when its graph is above the x-axis. We notice that this happens in two regions of the graph:
From -4 to -3
From -1 to 4
Therefore, the function is positive in:
[tex]\lbrack-4,-3)\cup(-1,4)[/tex]
c.
The function is zero when the graph intersect the x-axis; from the graph we have that the function is zero for:
[tex]\begin{gathered} x=-3 \\ x=-1 \\ x=4 \end{gathered}[/tex]
