As given by the question
There are given that the function:
Now,
According to the answer to question #1 and the graph of the function:
It is the area under the curve from x = 0 and x = 3;
So,
Some of it is below the x-axis means negative area and some of it is above the x-axis which means positive area.
Then,
Yes, they will cancel out and the integral gives the exact net result.
Explained!