[SOLVED] Cubic Functions, quick question. Please help :)

I was assigned a project from my online algebra II class and I've done the project and answered most of the questions but I'm stuck on a few of them that aren't really explained in my lesson. Would really appreciate any help.

As reference here is the assignment:

Equipment

Graphing Tool (provided), 8 pieces of 8.5 x 11 paper, Scissors, Ruler, Tape, Pencil

Procedure

1. Cut each of the 8 pieces of paper into squares measuring 8 inches by 8 inches.

2. Using a pencil and ruler, mark each side off in 1/2 inch increments so that you have created a piece of graph paper that has

16 squares by 16 squares. Repeat this procedure for all 8 pieces of paper.

3. Take one sheet of graph paper and cut out one square out of each of the 4 corners. Fold up the 4 sides to create a box

(without a lid) that has 14 squares across the bottom and has a height of 1 square up. You may want to tape the sides in

place. This is your first of 8 boxes.

4. Repeat step #3 cutting 1 inch squares from each of the 4 corners and folding up the sides. Continue with the remaining 6

pieces of paper increasing the size of the squares that you will cut out by 1/2 inch. Can the last piece of paper have 4 inch

squares cut from each corner? Why or why not?

5. Create a data table like the example data table below.

Note: The measurements are in inches, not squares. Each square is 1/2 inch. Volume should be given in cubic inches.

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QUESTION:

I have done the data table and don't need help with that however these are the questions I'm stuck on.

5. Where does your function graph intersect the x-axis? These points are called the zeros of the function. Notice that you are able to see the zeros in the graph of the function but not in the graph of your actual data points. What is the reason for that? Think about the differences between real data and the graph of an equation.

I said that the graph intersects at (0,0) [Link to the graph I made: http://i43.tinypic.com/2ir3v5j.png] but I don't understand how to explain the reason why and where I can go to find out about how to determine that.

2nd Question: What does the highest point of a cubic graph represent?

Again I would really appreciate any help. Thanks in advance!