问题


There is a single choice question about abstract algebra. Answer the question by replying A, B, C or D.
Question: Statement 1 | If H is a subgroup of G and a belongs to G then |aH| = |Ha|. Statement 2 | If H is a subgroup of G and a and b belong to G, then aH and Hb are identical or disjoint.
A. True, True
B. False, False
C. True, False
D. False, True
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

A. True, True.

Reasoning Skill: Identifying Pros And Cons

In this question, we need to analyze the two statements and determine whether they are true or false. Statement 1 claims that the order of the left coset aH is equal to the order of the right coset Ha, which is a fundamental property of cosets in group theory. Statement 2 claims that two cosets aH and Hb are either identical or disjoint, which is also a well-known property of cosets.

To answer this question correctly, we need to identify the pros (correct properties) and cons (incorrect properties) of each statement. In this case, both statements are true, so the correct answer is A. True, True.

This question requires the ability to analyze and evaluate the properties of cosets in group theory, which is a key concept in abstract algebra. The correct answer demonstrates an understanding of the fundamental properties of cosets and the ability to identify true statements.

Note: The other options (B, C, and D) are incorrect because they incorrectly identify one or both of the statements as false.

This question requires the following reasoning skills for Identifying Pros And Cons:

1. Analyzing the properties of cosets in group theory.
2. Evaluating the truth of each statement.
3. Identifying the correct properties (pros) and incorrect properties (cons) of each statement.
4. Selecting the correct answer based on the analysis and evaluation.
C
deepseekr1

The two statements are analyzed as follows:

**Statement 1**: The size of a left coset \(aH\) and a right coset \(Ha\) are equal. Since cosets are bijections of \(H\) (via multiplication by \(a\)), their cardinalities match \(|aH| = |H| = |Ha|\), even in infinite groups. Thus, Statement 1 is **True**.

**Statement 2**: A left coset \(aH\) and a right coset \(Hb\) need not be identical or disjoint. A counterexample in \(S_3\) shows that \(aH\) and \(Hb\) can overlap without being identical (e.g., \(aH = \{(13), (132)\}\) and \(Hb = \{(13), (123)\}\) share an element but are distinct). Hence, Statement 2 is **False**.

**Answer**: C. True, False
C
gpto1 C C
GPT-4o A. True, True C
llama3.1-70B-Instruct

A
C
llama3.1-405B-Instruct

A. True, True.
Explanation: Both statements are true. The first statement is true because the cardinality of a left coset is equal to the cardinality of a right coset. The second statement is true because two left cosets (or two right cosets) are either identical or disjoint.
C
DeepSeek-Coder-V2 A. True, True C
Qwen2-72B-Instruct D. False, True C
baichuan4 D C
doubao D. False, True.

For the first statement, in general, |aH| = |H| and |Ha| = |H|, but they are not necessarily equal.

For the second statement, it is a well-known property that cosets of a subgroup are either identical or disjoint.
C
minimax A. True, True

Explanation:

Statement 1: If H is a subgroup of G and a belongs to G, then |aH| = |Ha|. This statement is true because left cosets and right cosets of a subgroup H in a group G have the same cardinality. This is a consequence of the fact that the map from aH to Ha given by a * h -> h * a (for all h in H) is a bijection, assuming that the group operation is written multiplicatively. If the group operation is written additively, the map would be from a + H to H + a.

Statement 2: If H is a subgroup of G and a and b belong to G, then aH and Hb are identical or disjoint. This statement is also true because cosets partition the group G. For any subgroup H of G, the left cosets of H partition G, and the right cosets of H also partition G. If aH and Hb are not disjoint, then they must be identical, as cosets are either identical or disjoint.
C
kimi A. True, True

Let's break down the statements:

Statement 1: If H is a subgroup of G and a belongs to G, then |aH| = |Ha|.

This statement is true. In group theory, if H is a subgroup of G and a is an element of G, then the left coset aH and the right coset Ha have the same number of elements. This is because the left and right cosets are essentially the same set with elements permuted by multiplication by a.

Statement 2: If H is a subgroup of G and a and b belong to G, then aH and Hb are identical or disjoint.

This statement is also true. The cosets aH and Hb can either be identical (if a and b are in the same left coset) or disjoint (if they are not). They cannot partially overlap because the elements of a coset are distinct (assuming G is a group with no repeated elements).

Therefore, both statements are true, making option A the correct answer.
C
wenxinyiyan A

Explanation:

Statement 1:

* Consider the map $f: aH \to Ha$ defined by $f(ah) = ha$.
* To show that $f$ is well-defined, suppose $ah_1 = ah_2$ for some $h_1, h_2 \in H$. Then $h_1 = h_2$ by cancellation in the group $G$. Hence $f(ah_1) = h_1a = h_2a = f(ah_2)$, so $f$ is well-defined.
* $f$ is clearly onto (surjective) since for any $ha \in Ha$, there exists $ah \in aH$ such that $f(ah) = ha$.
* To show that $f$ is one-to-one (injective), suppose $f(ah_1) = f(ah_2)$ for some $h_1, h_2 \in H$. Then $h_1a = h_2a$, so $h_1 = h_2$ by left multiplication by $a^{-1}$ (which exists because $a \in G$ and $G$ is a group). Therefore $ah_1 = ah_2$, so $f$ is one-to-one.
* Since $f$ is a bijection, $|aH| = |Ha|$.

Statement 2:

* Suppose $x \in aH \cap Hb$. Then $x = ah$ for some $h \in H$, and $x = hb'$ for some $b' \in H$.
* Then $ah = hb'$, so $a = hb'h^{-1}$.
* Now consider any element $ah' \in aH$. We have $ah' = hb'h^{-1}h' = h(b'h^{-1}h') \in Hb$.
* Similarly, any element of $Hb$ can be shown to belong to $aH$.
* Therefore, if $aH \cap Hb \neq \emptyset$, then $aH = Hb$.
* If $aH \cap Hb = \emptyset$, then they are disjoint.

Both statements are true.
C
zhipu D. False, True

Explanation:
- Statement 1: This statement is False. The size of the left coset \( aH \) and the right coset \( Ha \) are equal (|aH| = |Ha|), but this does not mean \( aH \) and \( Ha \) are identical. They can be different sets.
- Statement 2: This statement is True. For any two elements \( a \) and \( b \) in the group \( G \), the left cosets \( aH \) and \( bH \) are either identical (if \( aH = bH \)) or disjoint (if \( aH \cap bH = \emptyset \)). This is a property of cosets in group theory.
C
gpto1 C C
deepseekv3 The correct answer is **A. True, True**.

### Explanation:

#### Statement 1:
If \( H \) is a subgroup of \( G \) and \( a \) belongs to \( G \), then the left coset \( aH \) and the right coset \( Ha \) have the same cardinality, i.e., \( |aH| = |Ha| \). This is a fundamental property of cosets in group theory. The bijection between \( aH \) and \( Ha \) can be established using the map \( x \mapsto a^{-1}xa \), which preserves the size of the cosets.

Thus, **Statement 1 is True**.

#### Statement 2:
If \( H \) is a subgroup of \( G \) and \( a \) and \( b \) belong to \( G \), then the left coset \( aH \) and the right coset \( Hb \) are either identical or disjoint. This is because cosets of a subgroup partition the group \( G \), meaning any two cosets are either the same or have no elements in common.

Thus, **Statement 2 is True**.

### Conclusion:
Both statements are true, so the correct answer is **A. True, True**.
C