# Homework Help: Boolean algebra

1. Feb 19, 2007

### Amith2006

1. The problem statement, all variables and given/known data

1) Simplify the following Boolean expression:
Y = ABCD – ABD

2. Relevant equations

3. The attempt at a solution

I simplified it in the following way:
Y = ABCD – ABD. (C + 1)
= - ABD
But the answer given in my book is ABD.

2. Feb 23, 2007

### RedSunflowers32

Typos are possible

Could be a typo in the back of the book. In my Discrete Math we are finding almost 20 errors per section. =o) Contact your teacher?

3. Feb 25, 2007

### Boole

Could you specify which textbook and which page? Thanks.

Boolean algebra deals solely in ones and zeroes. It has only three operators: addition, multiplication and negation. There can be no negative numbers. Namely, -1 is not an allowed number, so the concept of subtraction is meaningless is Boolean algebra.

Having said that, Y= ABCD – ABD has either a misprint – instead of +. In this case,
Y= ABCD + ABD = ABD(C+1)=ABD(1)=ABD

Or, possibly, – is given some special meaning.

4. Mar 5, 2007

### Amith2006

Sorry for the delayed reply. I was busy with my exams. It is a book by an Indian author. Basic Electronics by B.L.Theraja. I think u r right.The question should have been,
Y = ABD - ABCD
Isn't it?