# Property Help

• Nov 21st 2006, 12:20 PM
k1ll3rdr4g0n
Property Help
I have this problem:
a * (a + b) = a

And I can only use the commutative, distributive, identity, negation properties.

A hint that my teacher gives is to use is
a * a (a + b) = (a + 0) * (a + b)

Can anyone help me?
My teacher doesn't explain it well at all!
• Nov 21st 2006, 12:46 PM
Plato
You have to tell us more about what is going on here.
What is the definition of the operation *?
How does a(a+b) work or what does a(a+b) mean?
• Nov 21st 2006, 01:04 PM
k1ll3rdr4g0n
Quote:

Originally Posted by Plato
You have to tell us more about what is going on here.
What is the definition of the operation *?
How does a(a+b) work or what does a(a+b) mean?

Whops the hint is actually a * (a + b) = (a + 0) * (a + b)

But I think you got it.

* = and
+ = or
• Nov 21st 2006, 02:27 PM
Plato
This a simple Boolean Algebra.
This proof may or may not fit your text book.
[tex]This a simple Boolean Algebra.
This proof may or may not fit your text book.
$\begin{array}{rcl}
a*\left( {a + b} \right) & = & \left( {a + 0} \right)*\left( {a + b} \right)\quad \mbox{Identity Law} \\
& = & a + \left( {0*b} \right)\quad \mbox{Disributive Law} \\
& = & a + 0\quad \mbox{Null Law}l \\
& = & a\quad \mbox{Identity Law} \\
\end{array}
$