# Nested Quantifiers

• Oct 5th 2008, 07:29 PM
repcvt
Nested Quantifiers
I was confused with g).

Thx for comming.
• Oct 5th 2008, 11:57 PM
Opalg
$\exists x\,\forall y\, (y\ne x \Rightarrow M(x,y))$.
• Oct 6th 2008, 12:45 AM
repcvt
Thank U very much.
But
http://www.mathhelpforum.com/math-he...8b7d28f2-1.gif.

what's different with My anwser :
• Oct 6th 2008, 08:57 AM
Opalg
Quote:

Originally Posted by repcvt

The statement $\exists x\,\forall y\, (M(x,y)\wedge y\ne x)$ means that there is a student (x) who has emailed everyone in the class and who is different from everyone in the class. But that would mean in particular that x is different from himself/herself. Obviously that's not possible.

You could have given the alternative solution $\exists x\,\forall y\, ((y= x) \vee M(x,y))$ (meaning that either x=y or x has emailed y).
• Oct 6th 2008, 05:07 PM
repcvt
Quote:

Originally Posted by Opalg
The statement $\exists x\,\forall y\, (M(x,y)\wedge y\ne x)$ means that there is a student (x) who has emailed everyone in the class and who is different from everyone in the class. But that would mean in particular that x is different from himself/herself. Obviously that's not possible.

You could have given the alternative solution $\exists x\,\forall y\, ((y= x) \vee M(x,y))$ (meaning that either x=y or x has emailed y).

Understand it now.Thank U very much.BTW,How did U make that so good express like that

http://www.mathhelpforum.com/math-he...5ac0e526-1.gif

I mean how edit that image like that.look my express,that is so bad.I drawed it handly.:)
• Oct 6th 2008, 11:53 PM
Opalg
Quote:

Originally Posted by repcvt
How did U make that so good express like that

http://www.mathhelpforum.com/math-he...5ac0e526-1.gif

I mean how edit that image like that.

http://www.mathhelpforum.com/math-he...-tutorial.html