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Select the correct answer.

Consider the polynomials given below.
[tex]\[
\begin{array}{l}
P=x^4+3x^3+2x^2-x+2 \\
Q=\left(x^3+2x^2+3\right)\left(x^2-2\right)
\end{array}
\][/tex]

Determine the operation that results in the simplified expression below.
[tex]\[
x^5 + x^4 - 5x^3 - 3x^2 + x - 8
\][/tex]

A. [tex]\( PQ \)[/tex]
B. [tex]\( P - Q \)[/tex]
C. [tex]\( Q - P \)[/tex]
D. [tex]\( P + Q \)[/tex]

Sagot :

To determine which operation results in the simplified expression [tex]\( x^5 + x^4 - 5x^3 - 3x^2 + x - 8 \)[/tex], let's break down the problem step-by-step.

We are given the polynomials:
[tex]\[ P = x^4 + 3x^3 + 2x^2 - x + 2 \][/tex]
[tex]\[ Q = (x^3 + 2x^2 + 3)(x^2 - 2) \][/tex]

First, let's simplify [tex]\( Q \)[/tex]:
[tex]\[ Q = (x^3 + 2x^2 + 3)(x^2 - 2) \][/tex]
Multiplying these polynomials out:
[tex]\[ Q = x^3(x^2 - 2) + 2x^2(x^2 - 2) + 3(x^2 - 2) \][/tex]
Distribute each term:
[tex]\[ Q = x^5 - 2x^3 + 2x^4 - 4x^2 + 3x^2 - 6 \][/tex]
Combine like terms:
[tex]\[ Q = x^5 + 2x^4 - 2x^3 - x^2 - 6 \][/tex]

Now we look at which operation between [tex]\( P \)[/tex] and [tex]\( Q \)[/tex] yields [tex]\( x^5 + x^4 - 5x^3 - 3x^2 + x - 8 \)[/tex]. The possible operations are:
1. [tex]\( PQ \)[/tex]
2. [tex]\( P - Q \)[/tex]
3. [tex]\( Q - P \)[/tex]
4. [tex]\( P + Q \)[/tex]

Given the desired simplified expression, we compare the results of each operation:

1. [tex]\( PQ \)[/tex]:
- Multiplying [tex]\( P \)[/tex] and [tex]\( Q \)[/tex] yields a polynomial much more complex than the target polynomial and of a higher degree (likely degree 9). Therefore, [tex]\( PQ \)[/tex] is not correct.

2. [tex]\( P - Q \)[/tex]:
- Subtracting [tex]\( Q \)[/tex] from [tex]\( P \)[/tex]:
[tex]\[ P - Q = \left(x^4 + 3x^3 + 2x^2 - x + 2\right) - \left(x^5 + 2x^4 - 2x^3 - x^2 - 6\right) \][/tex]
- Simplify:
[tex]\[ P - Q = -x^5 - x^4 + 5x^3 + 3x^2 - x + 8 \][/tex]
- This transformation gives:
[tex]\[ P - Q = x^5 + x^4 - 5x^3 - 3x^2 + x - 8 \][/tex]

Following these steps, the simplified polynomial [tex]\( x^5 + x^4 - 5x^3 - 3x^2 + x - 8 \)[/tex] matches the expression found by computing [tex]\( Q - P \)[/tex]. Therefore, the correct operation is:

[tex]\[ \boxed{Q - P} \][/tex]

So, the correct answer is [tex]\( \text{C. } Q - P \)[/tex].