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 a group G and a belongs to G, then aH = Ha. Statement 2 | If H is normal of G and a belongs to G, then ah = ha for all h in H.
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 B B
deepseekr1

The analysis of both statements is as follows:

**Statement 1** claims that for any subgroup \( H \) of \( G \) and \( a \in G \), the left coset \( aH \) equals the right coset \( Ha \). This is only true if \( H \) is a **normal subgroup** of \( G \). However, the statement does not require \( H \) to be normal. A counterexample in \( S_3 \), where a non-normal subgroup (e.g., \( \{(1), (12)\} \)) shows \( aH \neq Ha \), proves the statement **false**.

**Statement 2** asserts that if \( H \) is normal in \( G \), then \( ah = ha \) for all \( h \in H \) and \( a \in G \). Normality ensures \( aH = Ha \), meaning for every \( h \in H \), there exists \( h' \in H \) such that \( ah = h'a \). However, this does **not** imply \( h = h' \) for all \( h \). A counterexample using \( H = A_3 \) (normal in \( S_3 \)) and \( a = (12) \in S_3 \) demonstrates \( ah \neq ha \), making the statement **false**.

Both statements are false.

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

Statement 1 is false. Consider the dihedral group D4. Let H = {e, h} and a = r. Then aH = {r, rh} and Ha = {r, hr}. Since r ≠ hr, aH ≠ Ha. Statement 2 is false. Consider the dihedral group D4. Let H = {e, r2} and a = r. Then H is normal in G. But r.r2 = r3 and r2.r = r. Since r3 ≠ r, we have ar ≠ ra.
B
llama3.1-405B-Instruct

A
B
DeepSeek-Coder-V2 B B
Qwen2-72B-Instruct D. False, True B
baichuan4 D. False, True B
doubao D. False, True.

The first statement is not generally true for all subgroups. But the second statement is a property of a normal subgroup.
B
minimax A. True, True

Explanation:
Statement 1 is true because if H is a subgroup of G, then for any element a in G, the left coset aH and the right coset Ha are related by the equation aH = Ha if and only if H is a normal subgroup of G. However, in general, without H being normal, the statement does not hold true.

Statement 2 is true because it is the definition of a normal subgroup. A subgroup H of a group G is said to be normal if for every element a in G and every element h in H, the equation ah = ha holds. This is exactly what Statement 2 is saying.
B
kimi D. False, True

Explanation:
Statement 1: If H is a subgroup of a group G and a belongs to G, then aH = Ha.
This statement is false. In general, the left coset aH and the right coset Ha are not necessarily equal unless H is a normal subgroup of G. A coset aH is the set of all elements of the form ah where h is in H, and a coset Ha is the set of all elements of the form ha where h is in H. If H is not a normal subgroup, then aH and Ha can be different.

Statement 2: If H is normal of G and a belongs to G, then ah = ha for all h in H.
This statement is true. If H is a normal subgroup of G, then for any element a in G and any element h in H, the element ah is in H and the element ha is also in H. This means that the operation of multiplying an element from G with an element from H on either side results in an element that is still in H, which is the definition of a normal subgroup.
B
wenxinyiyan D B
zhipu D. False, True

Explanation:
- Statement 1: If \( H \) is a subgroup of a group \( G \) and \( a \) belongs to \( G \), then \( aH \) (left coset of \( H \) by \( a \)) does not necessarily equal \( Ha \) (right coset of \( H \) by \( a \)) unless \( H \) is a normal subgroup. Thus, Statement 1 is False.
- Statement 2: If \( H \) is normal in \( G \) and \( a \) belongs to \( G \), then for all \( h \) in \( H \), \( ah = ha \). This is a defining property of normal subgroups. Thus, Statement 2 is True.

Therefore, the correct answer is D. False, True.
B
gpto1 B B
deepseekv3 The correct answer is **D. False, True**.

### Explanation:

**Statement 1**: "If \( H \) is a subgroup of a group \( G \) and \( a \) belongs to \( G \), then \( aH = Ha \)."
This statement is **False**.
The equality \( aH = Ha \) holds if and only if \( H \) is a **normal subgroup** of \( G \). For an arbitrary subgroup \( H \), this is not necessarily true.

**Statement 2**: "If \( H \) is normal in \( G \) and \( a \) belongs to \( G \), then \( ah = ha \) for all \( h \) in \( H \)."
This statement is **True**.
If \( H \) is normal in \( G \), then for any \( a \in G \) and \( h \in H \), we have \( ah = ha \). This is the definition of a normal subgroup.

Thus, the correct answer is **D. False, True**.
B