# Homework Hints 5-1

### Note: Homework Hints are given only for the Level 1 and Level 2 problems.

However, as you go through the book be sure you look at all the examples in the text. If you need hints for the Level 3 problems, check some sources for help on the internet (see the LINKS for that particular section). As a last resort, you can call the author at (707) 829-0606.

On the other hand, the problems designated “Problem Solving” generally require techniques that do not have textbook examples.

There are many sources for homework help on the internet.

Algebra.help
Here is a site where technology meets mathematics. You can search a particular topic or choose lessons, calculators, worksheets for extra practice or other resources.
http://www.algebrahelp.com/

Dr. Math is a registered trademark. This is an excellent site at which you can search to see if your question has been previously asked, or you can send your question directly to Dr. Math to receive an answer.
http://mathforum.org/dr.math/

Quick Math
This site provides online graphing calculators. This is especially useful if you do not have your own calculator.
http://www.quickmath.com/

The Math Forum @ Drexel
This site provides an internet mathematics library that can help if you need extra help. For additional homework help at this site, click one of the links in the right-hand column.
http://mathforum.org/

Problems 1-8
There are many problems throughout the text labeled IN YOUR OWN WORDS. Just relax; do not be afraid to give your opinion. For the most part, these questions do not have “right” or “wrong” answers. You should spend about five minutes in answering each of these questions.
Problems 9-14
Addition is accepted as an undefined term, but multiplication is defined as repeated addition. You need to carefully apply this definition for these problems. For example, the answer to Problem 9a is not 6, but rather is 2*3 = 3 + 3.
Problems 15-26
Review the definition of the associative and commutative properties. Remember that when the commutative property is used, the order in which the elements appear from left to right is changed, but the grouping is not changed. When the associative property is used, the elements are grouped differently, but the order in which they appear is not changed.
Problems 27-30
These problems are designed to test your understanding the commutative and associative properties in interesting everyday settings.
Problems 31-32
There are many problems throughout the text labeled IN YOUR OWN WORDS. Just relax; do not be afraid to give your opinion. For the most part, these questions do not have “right” or “wrong” answers. You should spend about five minutes in answering each of these questions.
Problems 33-34
These problems are discussing operations defined by table. Remember to read the column at the left first. In Problem 34, (-1) x is located in row 2 column 3. On the other hand  i x (-1) is located in row 3 column 2.
Problems 35-36
See Examples 1 and 2. A set is not closed for an operation if you can find one example of an answer that is not in the set. To show that a set is closed for an operation, you must look at the table of all outcomes.
Problems 37-40
These problems are defining a variety of operations, with focus on the commutative and associate properties. Remember, commutative is a property of order and associative is a property of grouping. Make sure you understand each defined operation before attempting to answer the question in the problem.
Problems 41-42
Make sure you understand the operation before proceeding.
Problem 41
A set is not closed for an operation if you can find one example of an answer that is not in the set. To show that a set is closed for an operation, you must look at the table of all outcomes.
Problem 42
Remember, the associate property is a grouping property and the commutative property is a property of order.
Problems 43-44
Make sure you understand the operation before proceeding. Carry out the requested operations and answer the questions.
Problem 45
a(b + c) = ab + ab is the distributive property for multiplication over addition.
We apply this property to the given operations:

a. Right over down would be:
a right (b down c) = (a right b) down (a right c)
Apply this for at least three sets of three natural numbers.

b. Down over right would be:
a down (b right c) = (a down b) right (a down c)
Apply this for at least three sets of three natural numbers.

Problems 46-47
Use the distributive property (see Example 4) for mental operations as in:
6 * 82 = 6*(80 + 2) = 6*80 + 6*2 = 480 + 12 = 492

You can do the above steps mentally.

Problem 48
Construct a multiplication table for the given set, and then look to see if the set is commutative or associative for this table. For the commutative property, there are four possibilities and for the associative property, there are eight possibilities.
Problem 49
Construct a multiplication table for the given set, and then look to see if the set is commutative or associative for this table. For the commutative property, there are nine possibilities and for the associative property, there are 27 possible ordered triplets. If you try several and look for patterns, you should be able to form a conclusion without trying all of them. However, to be absolutely certain, you will need to try all possibilities.
Problems 50-51
Remember, the even numbers are numbers of the form 2n; namely, {2, 4, 6, … }.

The odd numbers are of the form 2n + 1; namely, {1, 3, 5, … }.