I was confused with g).

Thx for comming.

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- Oct 5th 2008, 07:29 PMrepcvtNested Quantifiers
I was confused with g).

Thx for comming. - Oct 5th 2008, 11:57 PMOpalg
$\displaystyle \exists x\,\forall y\, (y\ne x \Rightarrow M(x,y))$.

- Oct 6th 2008, 12:45 AMrepcvt
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 AMOpalg
The statement $\displaystyle \exists x\,\forall y\, (M(x,y)\wedge y\ne x)$ 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 $\displaystyle \exists x\,\forall y\, ((y= x) \vee M(x,y))$ (meaning that*either*x=y*or*x has emailed y). - Oct 6th 2008, 05:07 PMrepcvt

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 PMOpalg