# Math Help - universe of discourse

1. ## universe of discourse

determine whether it is true when the universe of discourse to be R and using only symbols from the following list,,
this question is about AND OR conjunction ,disjunctions,,
details about question are in the attachment,,
i can't type the symbols,,
any help is appreciated.
thank you

2. Originally Posted by ives
determine whether it is true when the universe of discourse to be R and using only symbols from the following list,,
this question is about AND OR conjunction ,disjunctions,,
details about question are in the attachment,,
i can't type the symbols,,
any help is appreciated.
thank you
For all who cannot read the attachement it says
$\left( {\forall x} \right)\left( {\exists y} \right)\left[ {\left( {x = yy} \right) \vee \left( {yy + x = 0} \right)} \right]$
Is that true on the domain, $\mathbb{Z}$ or on $\mathbb{R}$.
On $\mathbb{Z}$ let $x=-3$. Is it true?

What about on $\mathbb{R}$?

3. i get a question, is the domain for x=yy affect the domain of yy+x=0

4. x = yy has all real numbers as its domain.
yy + x = 0 <=> x = -yy has all real numbers as its domain as well.

(graph these parabolas for a graphical arguement)

5. domain for x=yy can't be all real numbers , cuz yy>=0

6. Sorry, let me add an extra step.

If the domain refers to the x-axis, then all the real numbers are the domain (no restriction on x)
The range would then be the y-axis, which has a limitation, which you mentioned to be yy>=0, or specifically, that y > 0.