# What is this equation in simplified form

Discussion in 'Math' started by mentat, Apr 3, 2010.

1. ### mentat Thread Starter New Member

Mar 22, 2010
9
0
f = d'[b + (c xor a)'] + dcb'

Also, if only a and c are active high, and the rest are active low, what changes have to be made when building the circuit?

2. ### redlight000 Member

Feb 26, 2010
66
2
Looks like & Im not a maths expert, no way near,,

if look f=freq d< maybe decibel, c=capacitance and Im sure xor a is " xor a is a xor a Lgoic gate.. the dcb it looks like you have to add it..

sorry this is a bit of a flimsy answer... eek hope Im not totally wrong!!!
if you send the complete formular, it may throw more light on it" For the maths wizzes on here they are really good sgtwookie for one..
regards
redlight

3. ### mentat Thread Starter New Member

Mar 22, 2010
9
0
All the letters are just variables. They don't stand for anything.

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
Looks like a logic expression to me.

d' is the same as (not d) the dash being used to indicated negation.

All the letters are boolean or logic variables.

5. ### mentat Thread Starter New Member

Mar 22, 2010
9
0
Yes, this is a boolean logic equation that I am trying to simplify.

6. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
So where have you got to with it?

We don't do homework for people here, but will help if you show some working up to where you are stuck.

7. ### mentat Thread Starter New Member

Mar 22, 2010
9
0

d'[b + (c xor a)'] + dcb'
d'[b + c'a + ca'] + dcb'
d'b + d'c'a + d'ca' + dcb'

8. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
Well done that's always the best way.

9. ### mentat Thread Starter New Member

Mar 22, 2010
9
0
Can someone at least verify it's right?

10. ### zgozvrm Member

Oct 24, 2009
115
2
You should be able to verify it yourself. Make a truth table for each. Is the outcome of each truth table the same? If so, then you were successful.

Unfortunately, this is not the case...

Try, for example, the case where:
a = false
b = false
c = false
d = false

In this case f = true and g = false, therefore f ≠ g

Last edited: Sep 27, 2010
11. ### Georacer Moderator

Nov 25, 2009
5,151
1,266
Careful: (C XOR A)=C'A+CA'. So there is no way that (C XOR A)'=CA'+C'A. It's just the same expression in reverse.

The correct answer is CA+C'A'. But please post the proof as an exercise for yourself. Are you familia with the deMorgan's theorem? It is a must if you want to understand boolean expression conversion.