   Chapter 6.4, Problem 13ES ### Discrete Mathematics With Applicat...

5th Edition
EPP + 1 other
ISBN: 9781337694193

#### Solutions

Chapter
Section ### Discrete Mathematics With Applicat...

5th Edition
EPP + 1 other
ISBN: 9781337694193
Textbook Problem
1 views

# Exercises 12-15 provide an outline for a proof that the associative laws, which were included as an axiom for a Boolean algebra, can be derived from the other four axioms. The outline is from Introduction to Boolean Algebra by S. Givant and P. Halmos, Springer, 2009. In order to avoid unneeded parentheses, assume that. Takes precedence over +. The absorption law for + states that for all elements a and b in a Boolean algebra, a · b + a = a . Prove this law without using the associative law and using only the other four axioms for a Boolean algebra plus the result of exercise 12.

To determine

To derive the absorption law for + using other four axioms of Boolean algebra instead of using associative law for +.

Explanation

Given information:

The absorption law for + states that for all elements a and b in a Boolean algebra ab+a=a.

Calculation:

There are total five axioms of the Boolean algebra which are listed in the following table.

 Axioms Addition (+) Multiplication (.) (1) Commutative laws a+b=b+a a⋅b=b⋅a (2) Associative laws (a+b)+c=a+(b+c) (a⋅b)⋅c=a⋅(b⋅c) (3) Distributive laws (a+b)⋅c=a⋅c+b⋅c (a⋅b)+c=(a+c)⋅(b+c) (4) Identity laws a+0=a a⋅1=a (5) Complement laws a+a'=1 a⋅a'=0

Now, we have to prove the absorption law for + which is ab+a=a, for all elements a and b.

Consider the left hand side of the equation and apply the following axioms in order −

LHS=ab+a=ab+a1{x1=xusing Axiom 4}=a(b+1){(a+b)c=ac+bcusing Axiom 3}.....

### Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

#### The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started 