A)
Start by graphing the function on the different intervals.
For this, we graph as if they were independent functions and then join them on the same graph.
for x<4
for x>=4
then, for g(x)
B)
To find the x-intercepts:
equal g(x) to 0.
for x<4
for x>=4
then, for g(x)
For g(x) the x-intercepts are -4, 0 and 19
C)
finally, using the graph we can see that the function is positive in the intervals [-4,0)∪[4,19) because in these intervals g(x) is above the x-axis.