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One of the factors of the polynomial [tex]x^3 - 5x^2[/tex] is [tex]x + 3[/tex]. What is the other factor?

A. [tex]x^2 - 8x + 24 + \frac{72}{x + 3}[/tex]

B. [tex]x^2 - 8x + 24[/tex]

C. [tex]x^2 - 8x + 24 - \frac{72}{x + 3}[/tex]

D. [tex]x^3 - 8x^2 + 24x - 72[/tex]

Sagot :

To determine the other factor of the polynomial [tex]\( x^3 - 5x^2 \)[/tex] given that one of the factors is [tex]\( x + 3 \)[/tex], we need to perform polynomial division.

Here's how the steps of the polynomial division process work:

1. Divide the highest degree term of the polynomial by the highest degree term of the divisor:
[tex]\[ \frac{x^3}{x} = x^2 \][/tex]

2. Multiply the result by the divisor and subtract it from the original polynomial to find the new polynomial to be divided:
[tex]\[ (x^2) \cdot (x + 3) = x^3 + 3x^2 \][/tex]
[tex]\[ x^3 - 5x^2 - (x^3 + 3x^2) = -8x^2 \][/tex]

3. Repeat the division with the new polynomial:
[tex]\[ \frac{-8x^2}{x} = -8x \][/tex]

4. Multiply the result by the divisor and subtract it from the polynomial:
[tex]\[ (-8x) \cdot (x + 3) = -8x^2 - 24x \][/tex]
[tex]\[ -8x^2 - (-8x^2 - 24x) = 24x \][/tex]

5. Repeat the division with the new polynomial:
[tex]\[ \frac{24x}{x} = 24 \][/tex]

6. Multiply the result by the divisor and subtract it from the polynomial:
[tex]\[ (24) \cdot (x + 3) = 24x + 72 \][/tex]
[tex]\[ 24x - (24x + 72) = -72 \][/tex]

7. The result of the division gives us the quotient [tex]\( x^2 - 8x + 24 \)[/tex] and a remainder of [tex]\( -72 \)[/tex].

So the polynomial [tex]\( x^3 - 5x^2 \)[/tex] can be expressed as:
[tex]\[ (x + 3)(x^2 - 8x + 24) + (-72) \][/tex]

Thus, the closest option without the remainder factor is:
[tex]\[ \boxed{x^2 - 8x + 24} \][/tex]

Therefore, the correct answer is:

B. [tex]\( x^2 - 8x + 24 \)[/tex]