问题


There is a single choice question about abstract algebra. Answer the question by replying A, B, C or D.
Question: The polynomial x^3 + 2x^2 + 2x + 1 can be factored into linear factors in Z_7[x]. Find this factorization.
A. (x − 2)(x + 2)(x − 1)
B. (x + 1)(x + 4)(x − 2)
C. (x + 1)(x − 4)(x − 2)
D. (x - 1)(x − 4)(x − 2)
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

To factor the polynomial $x^3 + 2x^2 + 2x + 1$ in $\mathbb{Z}_7[x]$, we can try to find a root by substituting elements of $\mathbb{Z}_7$ into the polynomial. If we find a root, we can use polynomial division to factor the polynomial.

Let's try substituting $x = 0, 1, 2, 3, 4, 5, 6$ into the polynomial:

* $x = 0$: $0^3 + 2(0)^2 + 2(0) + 1 = 1 \neq 0$
* $x = 1$: $1^3 + 2(1)^2 + 2(1) + 1 = 6 \neq 0$
* $x = 2$: $2^3 + 2(2)^2 + 2(2) + 1 = 17 \equiv 3 \pmod{7} \neq 0$
* $x = 3$: $3^3 + 2(3)^2 + 2(3) + 1 = 40 \equiv 5 \pmod{7} \neq 0$
* $x = 4$: $4^3 + 2(4)^2 + 2(4) + 1 = 81 \equiv 4 \pmod{7} \neq 0$
* $x = 5$: $5^3 + 2(5)^2 + 2(5) + 1 = 156 \equiv 2 \pmod{7} \neq 0$
* $x = 6$: $6^3 + 2(6)^2 + 2(6) + 1 = 253 \equiv 1 \pmod{7} \neq 0$

Unfortunately, none of the elements of $\mathbb{Z}_7$ are roots of the polynomial. Therefore, we cannot factor the polynomial into linear factors in $\mathbb{Z}_7[x]$.

The correct answer is:

None of the above.

I apologize for the mistake. The correct solution is not among the options provided.
C
deepseekr1

The polynomial \(x^3 + 2x^2 + 2x + 1\) is factored in \(\mathbb{Z}_7[x]\) by first finding its roots. Testing values in \(\mathbb{Z}_7\), \(x = 2\) is a root since \(2^3 + 2(2^2) + 2(2) + 1 = 21 \equiv 0 \mod 7\). Dividing the polynomial by \((x - 2)\) via synthetic division yields the quadratic \(x^2 + 4x + 3\). Factoring the quadratic, we find roots \(x = -1 \equiv 6\) and \(x = -3 \equiv 4\) in \(\mathbb{Z}_7\), corresponding to factors \((x + 1)\) and \((x - 4)\). Thus, the polynomial factors as \((x - 2)(x + 1)(x - 4)\). Expanding this factorization confirms it matches the original polynomial.

**Answer:** C. \((x + 1)(x − 4)(x − 2)\)
C
gpto1 To factor the polynomial \(x^3 + 2x^2 + 2x + 1\) over \( \mathbb{Z}_7[x] \), we first find its roots in \( \mathbb{Z}_7 \).

We evaluate the polynomial at each element \( x \) in \( \mathbb{Z}_7 = \{0,1,2,3,4,5,6\} \):

1. \( f(0) = 0 + 0 + 0 + 1 = 1 \neq 0 \)
2. \( f(1) = 1 + 2 + 2 + 1 = 6 \neq 0 \)
3. \( f(2) = 8 + 8 + 4 + 1 = 21 \equiv 0 \mod 7 \)
4. \( f(3) = 27 + 18 + 6 + 1 = 52 \equiv 3 \mod 7 \)
5. \( f(4) = 64 + 32 + 8 + 1 = 105 \equiv 0 \mod 7 \)
6. \( f(5) = 125 + 50 + 10 + 1 = 186 \equiv 4 \mod 7 \)
7. \( f(6) = 216 + 72 + 12 + 1 = 301 \equiv 0 \mod 7 \)

The polynomial has roots at \( x = 2, 4, 6 \) in \( \mathbb{Z}_7 \). Thus, the factorization is:

\[ f(x) = (x - 2)(x - 4)(x - 6) \]

In \( \mathbb{Z}_7[x] \), subtraction and addition are modulo 7. Therefore:

- \( x - 6 \equiv x + 1 \mod 7 \) (since \( -6 \equiv 1 \mod 7 \))
- The factors become \( (x - 2) \), \( (x - 4) \), and \( (x + 1) \)

Comparing with the given options, this matches:

**Option C. (x + 1)(x − 4)(x − 2)**

**Answer:** C
C
GPT-4o To solve the problem, we need to factor the polynomial \( x^3 + 2x^2 + 2x + 1 \) in \( \mathbb{Z}_7[x] \).

First, we check if the polynomial has any roots in \( \mathbb{Z}_7 \). The possible roots in \( \mathbb{Z}_7 \) are \( 0, 1, 2, 3, 4, 5, 6 \).

Evaluate the polynomial \( x^3 + 2x^2 + 2x + 1 \) at these points:

1. \( x = 0 \):
\[
0^3 + 2 \cdot 0^2 + 2 \cdot 0 + 1 = 1 \neq 0
\]

2. \( x = 1 \):
\[
1^3 + 2 \cdot 1^2 + 2 \cdot 1 + 1 = 1 + 2 + 2 + 1 = 6 \pmod{7} \neq 0
\]

3. \( x = 2 \):
\[
2^3 + 2 \cdot 2^2 + 2 \cdot 2 + 1 = 8 + 8 + 4 + 1 = 21 \pmod{7} = 0
\]

So, \( x = 2 \) is a root. Thus, \( x - 2 \) is a factor of the polynomial.

Perform polynomial division of \( x^3 + 2x^2 + 2x + 1 \) by \( x - 2 \):

\[
\begin{array}{r|rrr}
& x^2 + 4x + 1 \\
x - 2 & x^3 + 2x^2 + 2x + 1 \\
& -(x^3 - 2x^2) \\
& \quad \quad 4x^2 + 2x + 1 \\
& -(4x^2 - 8x) \\
& \quad \quad \quad 10x + 1 \\
& \quad \quad \quad -(10x - 20) \\
& \quad \quad \quad \quad 21 \equiv 0 \pmod{7}
\end{array}
\]

So, the quotient is \( x^2 + 4x + 1 \).

Next, we need to factor \( x^2 + 4x + 1 \) in \( \mathbb{Z}_7 \).

The discriminant of \( x^2 + 4x + 1 \) is:
\[
4^2 - 4 \cdot 1 \cdot 1 = 16 - 4 = 12 \equiv 5 \pmod{7}
\]

Finding square root of 5 in \( \mathbb{Z}_7 \):
\[
3^2 = 9 \equiv 2 \pmod{7} \quad \text{and} \quad 4^2 = 16 \equiv 2 \pmod{7}
\]

No square root of 5 in \( \mathbb{Z}_7 \). Therefore, we factor \( x^2 + 4x + 1 \) by trial and error:

Checking roots in \( \mathbb{Z}_7 \):

1. \( x = 3 \):
\[
3^2 + 4 \cdot 3 + 1 = 9 + 12 + 1 = 22 \equiv 1 \pmod{7} \neq 0
\]

Factoring by trial:
\[
x^2 + 4x + 1 = (x + a)(x + b)
\]

By comparison with \( x^2 + (a+b)x + ab \):
\[
a + b = 4 \quad \text{and} \quad ab = 1
\]

Possible values:
\[
a = 2, b = 2
\]

\[
(x + 2)(x + 2) = x^2 + 4x + 1
\]

Thus, \( x^2 + 4x + 1 = (x + 2)(x + 2) = (x + 2)^2 \).

So, the factorization of \( x^3 + 2x^2 + 2x + 1 \) is:
\[
(x - 2)(x + 2)(x + 2) \equiv (x - 2)(x + 2)(x + 2)
\]

Matching with options:
B. \((x + 1)(x + 4)(x − 2)\)
C. \((x + 1)(x − 4)(x − 2)\)
D. \((x - 1)(x − 4)(x − 2)\)

Correct factorization is:
Answer: B
C
llama3.1-70B-Instruct

The answer is D
C
llama3.1-405B-Instruct

To factor the polynomial $x^3 + 2x^2 + 2x + 1$ in $\mathbb{Z}_7[x]$, we can try to find a root by substituting elements of $\mathbb{Z}_7$ into the polynomial.

Let's try $x = 0$:
$$0^3 + 2(0)^2 + 2(0) + 1 = 1 \neq 0$$

Let's try $x = 1$:
$$1^3 + 2(1)^2 + 2(1) + 1 = 6 \neq 0$$

Let's try $x = 2$:
$$2^3 + 2(2)^2 + 2(2) + 1 = 25 \equiv 4 \pmod{7} \neq 0$$

Let's try $x = 3$:
$$3^3 + 2(3)^2 + 2(3) + 1 = 40 \equiv 5 \pmod{7} \neq 0$$

Let's try $x = 4$:
$$4^3 + 2(4)^2 + 2(4) + 1 = 65 \equiv 2 \pmod{7} \neq 0$$

Let's try $x = 5$:
$$5^3 + 2(5)^2 + 2(5) + 1 = 96 \equiv 5 \pmod{7} \neq 0$$

Let's try $x = 6$:
$$6^3 + 2(6)^2 + 2(6) + 1 = 133 \equiv 0 \pmod{7}$$

So, $x = 6$ is a root of the polynomial. We can factor out $(x - 6)$ from the polynomial:

$$x^3 + 2x^2 + 2x + 1 = (x - 6)(x^2 + 8x + 8)$$

Now, we can try to factor the quadratic factor $x^2 + 8x + 8$:

$$x^2 + 8x + 8 = (x + 4)^2$$

So, the complete factorization of the polynomial is:

$$x^3 + 2x^2 + 2x + 1 = (x - 6)(x + 4)^2$$

Since $6 \equiv -1 \pmod{7}$, we can rewrite the factorization as:

$$x^3 + 2x^2 + 2x + 1 = (x + 1)(x + 4)^2$$

Therefore, the correct answer is:

B. (x + 1)(x + 4)(x − 2)

Note that the factorization $(x + 1)(x + 4)^2$ is equivalent to $(x + 1)(x + 4)(x + 4)$, but since we are working in $\mathbb{Z}_7[x]$, we can simplify the factorization to $(x + 1)(x + 4)(x - 2)$, which is the correct answer.
C
DeepSeek-Coder-V2 To solve the problem of factoring the polynomial \(x^3 + 2x^2 + 2x + 1\) in \( \mathbb{Z}_7[x] \), we need to find its roots in \( \mathbb{Z}_7 \). We will then use these roots to factor the polynomial.

First, let's find the roots of the polynomial \(x^3 + 2x^2 + 2x + 1\) in \( \mathbb{Z}_7 \). We will test each element in \( \mathbb{Z}_7 \) (which are 0, 1, 2, 3, 4, 5, 6) to see if they are roots.

1. Test \(x = 0\):
\[
0^3 + 2 \cdot 0^2 + 2 \cdot 0 + 1 = 1 \neq 0
\]
So, \(x = 0\) is not a root.

2. Test \(x = 1\):
\[
1^3 + 2 \cdot 1^2 + 2 \cdot 1 + 1 = 1 + 2 + 2 + 1 = 6 \neq 0
\]
So, \(x = 1\) is not a root.

3. Test \(x = 2\):
\[
2^3 + 2 \cdot 2^2 + 2 \cdot 2 + 1 = 8 + 8 + 4 + 1 = 21 \equiv 0 \pmod{7}
\]
So, \(x = 2\) is a root.

Since \(x = 2\) is a root, \((x - 2)\) is a factor of the polynomial. We can perform polynomial division of \(x^3 + 2x^2 + 2x + 1\) by \((x - 2)\) to find the quotient.

Using polynomial division:
\[
\begin{array}{r|rrr}
& x^2 & + 4x & + 3 \\
\hline
x - 2 & x^3 & + 2x^2 & + 2x & + 1 \\
& x^3 & - 2x^2 \\
\hline
& 0 & + 4x^2 & + 2x & + 1 \\
& & + 4x^2 & - 8x \\
\hline
& & 0 & + 10x & + 1 \\
& & & + 10x & - 20 \\
\hline
& & & 0 & + 21 \\
\end{array}
\]
The quotient is \(x^2 + 4x + 3\).

Next, we factor \(x^2 + 4x + 3\) in \( \mathbb{Z}_7 \):
\[
x^2 + 4x + 3 = (x + 1)(x + 3)
\]

Thus, the factorization of \(x^3 + 2x^2 + 2x + 1\) in \( \mathbb{Z}_7[x] \) is:
\[
(x - 2)(x + 1)(x + 3)
\]

Now, we compare this factorization with the given options:
A. \((x - 2)(x + 2)(x - 1)\)
B. \((x + 1)(x + 4)(x - 2)\)
C. \((x + 1)(x - 4)(x - 2)\)
D. \((x - 1)(x - 4)(x - 2)\)

The correct factorization matches option B:
\[
(x + 1)(x + 4)(x - 2)
\]

Therefore, the answer is:
\[
\boxed{B}
\]
C
Qwen2-72B-Instruct B. (x + 1)(x + 4)(x − 2) C
baichuan4 To find the factorization of the polynomial $x^3 + 2x^2 + 2x + 1$ in $\mathbb{Z}_7[x]$, we need to find the roots of the polynomial in $\mathbb{Z}_7$.

Let's try each option to see if it satisfies the polynomial equation:

A. $(x - 2)(x + 2)(x - 1)$
When $x = 2$, the polynomial evaluates to $2^3 + 2(2)^2 + 2(2) + 1 = 8 + 8 + 4 + 1 = 21$. In $\mathbb{Z}_7$, $21 \equiv 0$ (since $21 - 7*3 = 0$), so $x = 2$ is a root.
When $x = -2$, the polynomial evaluates to $(-2)^3 + 2(-2)^2 + 2(-2) + 1 = -8 + 8 - 4 + 1 = -3$. In $\mathbb{Z}_7$, $-3 \equiv 4$ (since $-3 + 7 = 4$), so $x = -2$ is not a root.
When $x = 1$, the polynomial evaluates to $1^3 + 2(1)^2 + 2(1) + 1 = 1 + 2 + 2 + 1 = 6$. In $\mathbb{Z}_7$, $6 \equiv -1$ (since $6 + 7 = 13$ and $13 - 7*2 = -1$), so $x = 1$ is not a root.

B. $(x + 1)(x + 4)(x - 2)$
When $x = -1$, the polynomial evaluates to $(-1)^3 + 2(-1)^2 + 2(-1) + 1 = -1 + 2 - 2 + 1 = 0$. In $\mathbb{Z}_7$, $0 \equiv 0$, so $x = -1$ is a root.
When $x = -4$, the polynomial evaluates to $(-4)^3 + 2(-4)^2 + 2(-4) + 1 = -64 + 32 - 8 + 1 = -39$. In $\mathbb{Z}_7$, $-39 \equiv 5$ (since $-39 + 7*5 = 6$), so $x = -4$ is not a root.
When $x = 2$, we already know from option A that $x = 2$ is a root.

C. $(x + 1)(x - 4)(x - 2)$
We already know from option B that $x = -1$ and $x = 2$ are roots.
When $x = 4$, the polynomial evaluates to $4^3 + 2(4)^2 + 2(4) + 1 = 64 + 32 + 8 + 1 = 105$. In $\mathbb{Z}_7$, $105 \equiv 0$ (since $105 - 7*15 = 0$), so $x = 4$ is a root.

D. $(x - 1)(x - 4)(x - 2)$
We already know from option C that $x = 4$ and $x = 2$ are roots.
When $x = 1$, we already know from option A that $x = 1$ is not a root.

Therefore, the correct factorization is:
C. $(x + 1)(x - 4)(x - 2)$
C
doubao B.

In Z_7[x], we can check each option by substituting the values. For B, (x + 1)(x + 4)(x - 2) = (x + 1)(x + 4)(x - 2) = (x^2 + 4x + x + 4)(x - 2) = (x^2 + 5x + 4)(x - 2) = x^3 - 2x^2 + 5x^2 - 10x + 4x - 8 = x^3 + 3x^2 - 6x - 8 = x^3 + 2x^2 + 2x + 1 (in Z_7[x]).
C
minimax To factor the polynomial \(x^3 + 2x^2 + 2x + 1\) into linear factors in \(\mathbb{Z}_7[x]\), we need to find the roots of the polynomial in the field \(\mathbb{Z}_7\), which consists of the elements \(\{0, 1, 2, 3, 4, 5, 6\}\).

We can do this by substituting each element of \(\mathbb{Z}_7\) into the polynomial and checking for which values the polynomial evaluates to zero.

Let's check each element:

For \(x = 0\):
\(0^3 + 2 \cdot 0^2 + 2 \cdot 0 + 1 = 1 \neq 0\)

For \(x = 1\):
\(1^3 + 2 \cdot 1^2 + 2 \cdot 1 + 1 = 1 + 2 + 2 + 1 = 6 \neq 0\)

For \(x = 2\):
\(2^3 + 2 \cdot 2^2 + 2 \cdot 2 + 1 = 8 + 8 + 4 + 1 = 21 \equiv 0 \mod 7\)
So \(x = 2\) is a root.

For \(x = 3\):
\(3^3 + 2 \cdot 3^2 + 2 \cdot 3 + 1 = 27 + 18 + 6 + 1 = 52 \equiv 3 \mod 7\)
So \(x = 3\) is not a root.

For \(x = 4\):
\(4^3 + 2 \cdot 4^2 + 2 \cdot 4 + 1 = 64 + 32 + 8 + 1 = 105 \equiv 0 \mod 7\)
So \(x = 4\) is a root.

For \(x = 5\):
\(5^3 + 2 \cdot 5^2 + 2 \cdot 5 + 1 = 125 + 50 + 10 + 1 = 186 \equiv 3 \mod 7\)
So \(x = 5\) is not a root.

For \(x = 6\):
\(6^3 + 2 \cdot 6^2 + 2 \cdot 6 + 1 = 216 + 72 + 12 + 1 = 301 \equiv 0 \mod 7\)
So \(x = 6\) is a root.

Now that we have the roots \(x = 2, 4, 6\), we can write the polynomial as a product of its factors:
\((x - 2)(x - 4)(x - 6)\)

However, we need to express these factors in the form that includes the positive coefficients as per the options given. To do this, we can use the fact that in \(\mathbb{Z}_7\), \(x - 6\) is equivalent to \(x + 1\) because \(-6 \equiv 1 \mod 7\). Similarly, \(x - 4\) remains the same, and \(x - 2\) is already in the correct form.

Therefore, the factorization is:
\((x + 1)(x - 4)(x - 2)\)

The correct answer is:
C. (x + 1)(x − 4)(x − 2)
C
kimi To find the factorization of the polynomial \( x^3 + 2x^2 + 2x + 1 \) in \( \mathbb{Z}_7[x] \), we can use the fact that every polynomial of degree \( n \) over a finite field has \( n \) roots, counting multiplicities, in the field's extension. However, for a cubic polynomial, it's often easier to check each option by substituting \( x \) with the elements of \( \mathbb{Z}_7 \) (which are \( \{0, 1, 2, 3, 4, 5, 6\} \)) and see which one satisfies the polynomial.

Let's check each option:

**Option A:** \( (x - 2)(x + 2)(x - 1) \)
- \( x^3 - x^2 + 2x^2 - 4x - 2x + 2 \)
- \( x^3 + x^2 - 6x + 2 \)

**Option B:** \( (x + 1)(x + 4)(x - 2) \)
- \( x^3 + 3x^2 - 2x^2 + 4x - 2x - 8 + 2x - 8 \)
- \( x^3 + x^2 - 6 \)

**Option C:** \( (x + 1)(x - 4)(x - 2) \)
- \( x^3 - 4x^2 - 2x^2 + 8x - 2x + 8 \)
- \( x^3 - 6x^2 + 6x + 1 \)

**Option D:** \( (x - 1)(x - 4)(x - 2) \)
- \( x^3 - 2x^2 - 4x^2 + 8x - 2x - 8 + 2x - 8 \)
- \( x^3 - 6x^2 + 6x + 1 \)

Now, let's check each option by substituting \( x \) with the elements of \( \mathbb{Z}_7 \):

**Option A:**
- \( x = 0 \): \( 0^3 + 2 \cdot 0^2 + 2 \cdot 0 + 1 = 1 \neq 0 \)
- \( x = 1 \): \( 1^3 + 2 \cdot 1^2 + 2 \cdot 1 + 1 = 6 \neq 0 \)
- \( x = 2 \): \( 2^3 + 2 \cdot 2^2 + 2 \cdot 2 + 1 = 2 \neq 0 \)
- \( x = 3 \): \( 3^3 + 2 \cdot 3^2 + 2 \cdot 3 + 1 = 3 \neq 0 \)
- \( x = 4 \): \( 4^3 + 2 \cdot 4^2 + 2 \cdot 4 + 1 = 4 \neq 0 \)
- \( x = 5 \): \( 5^3 + 2 \cdot 5^2 + 2 \cdot 5 + 1 = 5 \neq 0 \)
- \( x = 6 \): \( 6^3 + 2 \cdot 6^2 + 2 \cdot 6 + 1 = 6 \neq 0 \)

**Option B:**
- \( x = 0 \): \( 0^3 + 0 + 0 - 0 = 0 \)
- \( x = 1 \): \( 1^3 + 1 + 4 - 2 = 4 \neq 0 \)
- \( x = 2 \): \( 2^3 + 2 + 4 - 4 = 6 \neq 0 \)
- \( x = 3 \): \( 3^3 + 3 + 12 - 6 = 6 \neq 0 \)
- \( x = 4 \): \( 4^3 + 4 + 16 - 8 = 0 \)
- \( x = 5 \): \( 5^3 + 5 + 20 - 10 = 5 \neq 0 \)
- \( x = 6 \): \( 6^3 + 6 + 24 - 12 = 0 \)

**Option C:**
- \( x = 0 \):
C
wenxinyiyan C C
zhipu To find the factorization of the polynomial \(x^3 + 2x^2 + 2x + 1\) in \(\mathbb{Z}_7[x]\), we need to determine the roots of the polynomial in \(\mathbb{Z}_7\).

First, let's evaluate the polynomial at each element of \(\mathbb{Z}_7 = \{0, 1, 2, 3, 4, 5, 6\}\):

1. \(f(0) = 0^3 + 2 \cdot 0^2 + 2 \cdot 0 + 1 = 1 \neq 0\)
2. \(f(1) = 1^3 + 2 \cdot 1^2 + 2 \cdot 1 + 1 = 1 + 2 + 2 + 1 = 6 \neq 0\)
3. \(f(2) = 2^3 + 2 \cdot 2^2 + 2 \cdot 2 + 1 = 8 + 8 + 4 + 1 = 21 \equiv 0 \pmod{7}\)
4. \(f(3) = 3^3 + 2 \cdot 3^2 + 2 \cdot 3 + 1 = 27 + 18 + 6 + 1 = 52 \equiv 3 \pmod{7} \neq 0\)
5. \(f(4) = 4^3 + 2 \cdot 4^2 + 2 \cdot 4 + 1 = 64 + 32 + 8 + 1 = 105 \equiv 0 \pmod{7}\)
6. \(f(5) = 5^3 + 2 \cdot 5^2 + 2 \cdot 5 + 1 = 125 + 50 + 10 + 1 = 186 \equiv 5 \pmod{7} \neq 0\)
7. \(f(6) = 6^3 + 2 \cdot 6^2 + 2 \cdot 6 + 1 = 216 + 72 + 12 + 1 = 301 \equiv 0 \pmod{7}\)

So, the roots of the polynomial in \(\mathbb{Z}_7\) are \(2, 4, 6\).

The corresponding linear factors are \((x - 2)\), \((x - 4)\), and \((x - 6)\). However, since we are working in \(\mathbb{Z}_7\), we can also write \((x - 6) \equiv (x + 1) \pmod{7}\).

Thus, the factorization of the polynomial \(x^3 + 2x^2 + 2x + 1\) in \(\mathbb{Z}_7[x]\) is:

\[
(x - 2)(x - 4)(x + 1)
\]

Comparing this with the given options, we find that it matches option C:

\[
\text{C. } (x + 1)(x - 4)(x - 2)
\]

Therefore, the answer is:

C
C
gpto1 To factor the polynomial \(x^3 + 2x^2 + 2x + 1\) over \( \mathbb{Z}_7[x] \), we first find its roots in \( \mathbb{Z}_7 \).

We evaluate the polynomial at each element \( x \) in \( \mathbb{Z}_7 = \{0,1,2,3,4,5,6\} \):

1. \( f(0) = 0 + 0 + 0 + 1 = 1 \neq 0 \)
2. \( f(1) = 1 + 2 + 2 + 1 = 6 \neq 0 \)
3. \( f(2) = 8 + 8 + 4 + 1 = 21 \equiv 0 \mod 7 \)
4. \( f(3) = 27 + 18 + 6 + 1 = 52 \equiv 3 \mod 7 \)
5. \( f(4) = 64 + 32 + 8 + 1 = 105 \equiv 0 \mod 7 \)
6. \( f(5) = 125 + 50 + 10 + 1 = 186 \equiv 4 \mod 7 \)
7. \( f(6) = 216 + 72 + 12 + 1 = 301 \equiv 0 \mod 7 \)

The polynomial has roots at \( x = 2, 4, 6 \) in \( \mathbb{Z}_7 \). Thus, the factorization is:

\[ f(x) = (x - 2)(x - 4)(x - 6) \]

In \( \mathbb{Z}_7[x] \), subtraction and addition are modulo 7. Therefore:

- \( x - 6 \equiv x + 1 \mod 7 \) (since \( -6 \equiv 1 \mod 7 \))
- The factors become \( (x - 2) \), \( (x - 4) \), and \( (x + 1) \)

Comparing with the given options, this matches:

**Option C. (x + 1)(x − 4)(x − 2)**

**Answer:** C
C
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