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What is the complete factorization of the polynomial below?

[tex]\[ x^3 + 8x^2 + 17x + 10 \][/tex]

A. [tex]\((x+1)(x-2)(x-5)\)[/tex]
B. [tex]\((x-1)(x-2)(x+5)\)[/tex]
C. [tex]\((x+1)(x+2)(x+5)\)[/tex]
D. [tex]\((x-1)(x+2)(x-5)\)[/tex]


Sagot :

Let's factorize the polynomial [tex]\( P(x) = x^3 + 8x^2 + 17x + 10 \)[/tex] step-by-step to find its complete factorization.

1. Identify the polynomial:
[tex]\[ P(x) = x^3 + 8x^2 + 17x + 10 \][/tex]

2. Check for possible rational roots: To factorize this polynomial, we can use the Rational Root Theorem which suggests that any rational root [tex]\( p/q \)[/tex] of the polynomial, where [tex]\( p \)[/tex] is a factor of the constant term (10) and [tex]\( q \)[/tex] is a factor of the leading coefficient (1), must be a candidate. Therefore, we have potential roots [tex]\( \pm 1, \pm 2, \pm 5, \pm 10 \)[/tex].

3. Test the potential rational roots:
Evaluate the polynomial for these potential roots to see which one is actually a root of the polynomial.

When we test these values, we eventually find that:
- For [tex]\( x = -1 \)[/tex]:
[tex]\[ P(-1) = (-1)^3 + 8(-1)^2 + 17(-1) + 10 = -1 + 8 - 17 + 10 = 0 \][/tex]
Therefore, [tex]\( x = -1 \)[/tex] is a root, so [tex]\( (x + 1) \)[/tex] is a factor.

4. Perform synthetic division: Next, we do synthetic division of [tex]\( P(x) \)[/tex] by [tex]\( x + 1 \)[/tex].

[tex]\[ \begin{array}{r|rrrr} -1 & 1 & 8 & 17 & 10 \\ & & -1 & -7 & -10 \\ \hline & 1 & 7 & 10 & 0 \\ \end{array} \][/tex]
The quotient is [tex]\( x^2 + 7x + 10 \)[/tex] with a remainder of 0, confirming that [tex]\( P(x) = (x + 1)(x^2 + 7x + 10) \)[/tex].

5. Factorize the quadratic: Now, we factorize the quadratic polynomial [tex]\( x^2 + 7x + 10 \)[/tex].

Find two numbers that multiply to 10 and add to 7. Those numbers are 2 and 5:
[tex]\[ x^2 + 7x + 10 = (x + 2)(x + 5) \][/tex]

6. Combine the factors:
[tex]\[ P(x) = (x + 1)(x + 2)(x + 5) \][/tex]

7. Verify the factorization: To ensure the factorization is correct, we can multiply the factors back together:
[tex]\[ (x + 1)(x + 2)(x + 5) \][/tex]
Multiply [tex]\( (x + 1)(x + 2) \)[/tex]:
[tex]\[ (x + 1)(x + 2) = x^2 + 3x + 2 \][/tex]
Then multiply [tex]\( (x^2 + 3x + 2)(x + 5) \)[/tex]:
[tex]\[ (x^2 + 3x + 2)(x + 5) = x^3 + 5x^2 + 3x^2 + 15x + 2x + 10 = x^3 + 8x^2 + 17x + 10 \][/tex]
The polynomial matches the original, confirming the factorization.

Therefore, the complete factorization of the polynomial [tex]\( x^3 + 8x^2 + 17x + 10 \)[/tex] is:
[tex]\[ \boxed{(x + 1)(x + 2)(x + 5)} \][/tex]
The correct answer is option C.