Question: Score: 8/20 Answered: 8/20
Question 12
Is $x + 2$ a factor of $x^3 + 3x^2 + 5x + 6$?
Select an answer The remainder when you divide is
Is $2x - 5$ a factor of $16x^4 + 56x^3 + 20x^2 + 8x - 1645$?
Select an answer The remainder when you divide is
Is $x - 1$ a factor of $x^5 + 5x^4 - 4x^3 + 5x^2 - 6x - 19$?
Select an answer The remainder when you divide is
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1. **Problem Statement:** Determine if the given polynomials are divisible by the given factors by finding the remainder when divided.
2. **Factor Theorem:** A polynomial $f(x)$ is divisible by $(x - a)$ if and only if $f(a) = 0$. The remainder when dividing by $(x - a)$ is $f(a)$.
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### Part 1: Is $x + 2$ a factor of $x^3 + 3x^2 + 5x + 6$?
3. Rewrite factor as $x - (-2)$, so $a = -2$.
4. Evaluate $f(-2) = (-2)^3 + 3(-2)^2 + 5(-2) + 6 = -8 + 12 - 10 + 6 = 0$.
5. Since $f(-2) = 0$, $x + 2$ is a factor.
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### Part 2: Is $2x - 5$ a factor of $16x^4 + 56x^3 + 20x^2 + 8x - 1645$?
6. Rewrite factor as $2x - 5 = 0
ightarrow x = \frac{5}{2}$.
7. Evaluate $f\left(\frac{5}{2}\right) = 16\left(\frac{5}{2}\right)^4 + 56\left(\frac{5}{2}\right)^3 + 20\left(\frac{5}{2}\right)^2 + 8\left(\frac{5}{2}\right) - 1645$.
8. Calculate powers:
$$\left(\frac{5}{2}\right)^2 = \frac{25}{4}, \quad \left(\frac{5}{2}\right)^3 = \frac{125}{8}, \quad \left(\frac{5}{2}\right)^4 = \frac{625}{16}$$
9. Substitute:
$$16 \times \frac{625}{16} + 56 \times \frac{125}{8} + 20 \times \frac{25}{4} + 8 \times \frac{5}{2} - 1645$$
10. Simplify each term:
$$625 + 875 + 125 + 20 - 1645 = 1000$$
11. Since remainder $= 1000 \neq 0$, $2x - 5$ is not a factor.
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### Part 3: Is $x - 1$ a factor of $x^5 + 5x^4 - 4x^3 + 5x^2 - 6x - 19$?
12. Here $a = 1$.
13. Evaluate $f(1) = 1 + 5 - 4 + 5 - 6 - 19 = -18$.
14. Since remainder $= -18 \neq 0$, $x - 1$ is not a factor.
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**Final answers:**
- $x + 2$ is a factor (remainder $0$).
- $2x - 5$ is not a factor (remainder $1000$).
- $x - 1$ is not a factor (remainder $-18$).