- #1
scorpius1782
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Homework Statement
I'm given a series of statements and I have to decide which one is true for my problem.
Are any of these equivalent to ##\exists ! xP(x)##?
##\exists x P(x)##^## \forall y(p(y)\implies y=x)##
##\exists x \forall y, x=y \implies p(y)##
##\exists x \forall y, p(y) \implies x=y ##
And true or false?
##\forall y \in \mathbb{N}, \exists x \in \mathbb{N}, x \leq y##
##\exists x \in \mathbb{N}, \forall y \in \mathbb{N}, x \leq y##
Homework Equations
The Attempt at a Solution
Just reading them properly is my big problem.
So for ##\exists x P(x)##^## \forall y(P(y)\implies y=x)##
it is saying there exists an 'x' satisfying P(x) and all 'y' then if P(y)=x then y=x.
I bolded the part I'm not sure about. It is the inclusion of the second element that throws me. It is the same for the true or false questions:
##\exists x \in \mathbb{N}, \forall y \in \mathbb{N}, x \leq y##
There exists an 'x' in the natural numbers that for all 'y' in the natural numbers ## x \leq y##
I would say this is true because x could be the same as y.
Thanks for any help.
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