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Multiply the following using the vertical multiplication method:

[tex]\[
\begin{array}{l}
x^2-5x+1 \\
x^2+2x+4
\end{array}
\][/tex]

A. [tex]\(3x^4 + x^3 + 10x^2 - 18x + 4\)[/tex]

B. [tex]\(3x^4 - x^3 + 3x^2 + 18x + 4\)[/tex]

C. [tex]\(3x^4 + x^3 + 3x^2 - 18x + 4\)[/tex]

D. [tex]\(3x^4 + x^3 + 10x^2 + x + 4\)[/tex]

Sagot :

To multiply the polynomials [tex]\(P(x) = x^2 - 5x + 1\)[/tex] and [tex]\(Q(x) = x^2 + 2x + 4\)[/tex], we will use the vertical multiplication method. Let's break it down step-by-step:

### Step 1: Multiply each term in [tex]\(P(x)\)[/tex] by each term in [tex]\(Q(x)\)[/tex]

First, distribute [tex]\(x^2\)[/tex] from [tex]\(Q(x)\)[/tex]:
[tex]\[ (x^2 \cdot (x^2 - 5x + 1)) = x^4 - 5x^3 + x^2 \][/tex]

Next, distribute [tex]\(2x\)[/tex] from [tex]\(Q(x)\)[/tex]:
[tex]\[ (2x \cdot (x^2 - 5x + 1)) = 2x^3 - 10x^2 + 2x \][/tex]

Finally, distribute [tex]\(4\)[/tex] from [tex]\(Q(x)\)[/tex]:
[tex]\[ (4 \cdot (x^2 - 5x + 1)) = 4x^2 - 20x + 4 \][/tex]

### Step 2: Add the results together, combining like terms

To combine the results, we align the terms with the same degree:

[tex]\[ \begin{array}{rcccccc} & x^4 & - 5x^3 & + x^2 & & & \\ + & & 2x^3 & - 10x^2 & + 2x & & \\ + & & & 4x^2 & - 20x & + 4 & \\ \hline \end{array} \][/tex]

Now, let's sum these expressions:

1. [tex]\(x^4\)[/tex] terms:
[tex]\[ x^4 \][/tex]

2. [tex]\(x^3\)[/tex] terms:
[tex]\[ -5x^3 + 2x^3 = -3x^3 \][/tex]

3. [tex]\(x^2\)[/tex] terms:
[tex]\[ x^2 - 10x^2 + 4x^2 = -5x^2 \][/tex]

4. [tex]\(x\)[/tex] terms:
[tex]\[ 2x - 20x = -18x \][/tex]

5. Constant terms:
[tex]\[ +4 \][/tex]

So, when we combine all like terms, we get:

[tex]\[ x^4 - 3x^3 - 5x^2 - 18x + 4 \][/tex]

### Step 3: Compare the result with the given choices

Let's rewrite the result:
[tex]\[ x^4 - 3x^3 - 5x^2 - 18x + 4 \][/tex]

Now, let’s check which provided choice matches our result:

A. [tex]\(3 x^4 + x^3 + 10 x^2 - 18 x + 4\)[/tex]

B. [tex]\(3 x^4 - x^3 + 3 x^2 + 18 x + 4\)[/tex]

C. [tex]\(3 x^4 + x^3 + 3 x^2 - 18 x + 4\)[/tex]

D. [tex]\(3 x^4 + x^3 + 10 x^2 + x + 4\)[/tex]

None of the provided options exactly match our result. Therefore, there might be an error. Let's re-evaluate our combination of like terms to ensure accuracy.

Correctly combining, our result should be:
[tex]\[ x^4 - 3x^3 - 5x^2 - 18x + 4 \][/tex]

Upon reviewing my work, it seems original calculations were correct. Thus, the correct answer should ideally match [tex]\( x^4 - 3x^3 - 5x^2 - 18x + 4 \)[/tex]. Based on given options, recheck provided choices; logically no option suits exactly our derived value properly.