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Question
Math
Posted 5 months ago
Determine whether the following are true or false. Explain why shortly.
Let X={1,2,{3,4},{1},{5}},Y={1,2,3}X=\{1,2,\{3,4\},\{1\},\{5\}\}, Y=\{1,2,3\}.
(a) {3,4,5}X\{3,4,5\} \subseteq X
(b) {1}P(X)\{1\} \in \mathcal{P}(X).
(c) {{5}}P(X)\{\{5\}\} \subseteq \mathcal{P}(X)
(d) {}P()\{\emptyset\} \in \mathcal{P}(\emptyset)
(e) {1,2}Y\{1,2\} \in Y.
(f) P(X)\emptyset \subseteq \mathcal{P}(X)
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Answer from Sia
Posted 5 months ago
Solution by Steps
step 1
To determine if {3,4,5}X\{3,4,5\} \subseteq X, we check if every element of {3,4,5}\{3,4,5\} is also an element of XX
step 2
The set XX is given as {1,2,{3,4},{1},{5}}\{1,2,\{3,4\},\{1\},\{5\}\}
step 3
The elements 3 and 4 are contained within a nested set {3,4}\{3,4\} in XX, not as individual elements, and 5 is contained within the nested set {5}\{5\}
step 4
Since {3,4,5}\{3,4,5\} are not individual elements of XX, the statement {3,4,5}X\{3,4,5\} \subseteq X is false
Answer
False
Key Concept
Subset Relation
Explanation
A set A is a subset of set B if every element of A is also an element of B. Nested elements are not considered individual elements of the set.
Solution by Steps
step 1
To determine if {1}P(X)\{1\} \in \mathcal{P}(X), we check if {1}\{1\} is an element of the power set of XX
step 2
The power set P(X)\mathcal{P}(X) contains all subsets of XX, including the individual elements as singleton sets
step 3
Since 11 is an element of XX, the singleton set {1}\{1\} is a subset of XX and thus an element of P(X)\mathcal{P}(X)
step 4
Therefore, the statement {1}P(X)\{1\} \in \mathcal{P}(X) is true
Answer
True
Key Concept
Power Set and Elements
Explanation
The power set of a set contains all possible subsets of the original set, including the singleton sets of its elements.
Solution by Steps
step 1
To determine if {{5}}P(X)\{\{5\}\} \subseteq \mathcal{P}(X), we check if the set containing the singleton set {5}\{5\} is a subset of the power set of XX
step 2
The power set P(X)\mathcal{P}(X) contains all subsets of XX, including the singleton set {5}\{5\}
step 3
Since {5}\{5\} is a subset of XX, the set {{5}}\{\{5\}\}, which contains {5}\{5\} as its only element, is a subset of P(X)\mathcal{P}(X)
step 4
Therefore, the statement {{5}}P(X)\{\{5\}\} \subseteq \mathcal{P}(X) is true
Answer
True
Key Concept
Subsets of Power Sets
Explanation
A set containing a subset of the original set is itself a subset of the power set of the original set.
Solution by Steps
step 1
To determine if {}P()\{\emptyset\} \in \mathcal{P}(\emptyset), we check if the set containing the empty set is an element of the power set of the empty set
step 2
The power set of the empty set P()\mathcal{P}(\emptyset) contains only two subsets: the empty set itself \emptyset and the set containing the empty set {}\{\emptyset\}
step 3
Therefore, the set {}\{\emptyset\} is an element of P()\mathcal{P}(\emptyset)
step 4
The statement {}P()\{\emptyset\} \in \mathcal{P}(\emptyset) is true
Answer
True
Key Concept
Power Set of the Empty Set
Explanation
The power set of the empty set contains the empty set itself and the set containing the empty set as its elements.
Solution by Steps
step 1
To determine if {1,2}Y\{1,2\} \in Y, we check if the set {1,2}\{1,2\} is an element of YY
step 2
The set YY is given as {1,2,3}\{1,2,3\}
step 3
The set {1,2}\{1,2\} is not an element of YY, but rather a subset of YY
step 4
Therefore, the statement {1,2}Y\{1,2\} \in Y is false
Answer
False
Key Concept
Element vs. Subset
Explanation
Being an element of a set and being a subset of a set are different; a set can be a subset without being an element.
Solution by Steps
step 1
To determine if P(X)\emptyset \subseteq \mathcal{P}(X), we check if the empty set is a subset of the power set of XX
step 2
The empty set \emptyset is a subset of every set, including the power set of any set
step 3
Therefore, the statement P(X)\emptyset \subseteq \mathcal{P}(X) is true
Answer
True
Key Concept
Empty Set as a Subset
Explanation
The empty set is universally a subset of any set, including the power set of any set.

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