MHB Write ⊆ or ⊄ in the space provided.

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The discussion focuses on determining whether to use the subset symbol (⊆) or the not a subset symbol (⊄) in various mathematical expressions. The first two expressions are confirmed to be correct, while clarification is provided on the third expression involving the power set of the empty set. The fourth expression compares Cartesian products of natural and integer numbers, with a consensus that the left side contains distinct elements not found on the right. Overall, the participants engage in correcting and confirming the appropriate symbols for the given mathematical relationships.
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Write ⊆ or in the space provided.

(3,5) _____ [3,5]
[-1,4] ____ (-1,4)
{∅} _____ P(∅)
N * Z ____ Z * NMy Solution)




 
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KOO said:
Write ⊆ or in the space provided.

(3,5) _____ [3,5]
[-1,4] ____ (-1,4)
{∅} _____ P(∅)
N * Z ____ Z * NMy Solution)





Hi KOO! :)

The first 2 are correct.

Edit: see Evgeny.Makarov's post for the 3rd.

As for the 4th, can I assume you intended $\mathbb N \times \mathbb Z \underline{\qquad} \mathbb Z \times \mathbb N$?
If so then the left hand side has elements like (1,1) and (1,-1), while the right hand side has elements like (-1,1) and (1,1)...
 
I assume the first two questions are about intervals on the real line. Then I agree.

KOO said:
{∅} _____ P(∅)
Note that P(∅) = {∅}.
 
Evgeny.Makarov said:
Note that P(∅) = {∅}.

Good point.
Slipped on that one.
 
There is a nice little variation of the problem. The host says, after you have chosen the door, that you can change your guess, but to sweeten the deal, he says you can choose the two other doors, if you wish. This proposition is a no brainer, however before you are quick enough to accept it, the host opens one of the two doors and it is empty. In this version you really want to change your pick, but at the same time ask yourself is the host impartial and does that change anything. The host...

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