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Which of the following is a factor of [tex]3x^3 + 18x^2 + 27x[/tex]?

A. [tex]9x[/tex]

B. [tex]x^3[/tex]

C. [tex]x + 3[/tex]

D. [tex]x - 3[/tex]


Sagot :

To determine which of the given choices are factors of the polynomial [tex]\(3x^3 + 18x^2 + 27x\)[/tex], we need to test each factor by dividing the polynomial by each choice and checking if the result is a polynomial with no remainder.

1. Testing [tex]\(9x\)[/tex]:

Dividing [tex]\(3x^3 + 18x^2 + 27x\)[/tex] by [tex]\(9x\)[/tex]:
[tex]\[ \frac{3x^3 + 18x^2 + 27x}{9x} = \frac{3x^3}{9x} + \frac{18x^2}{9x} + \frac{27x}{9x} = \frac{3}{9} x^2 + \frac{18}{9} x + \frac{27}{9} = \frac{1}{3} x^2 + 2x + 3 \][/tex]
The result, [tex]\(\frac{1}{3} x^2 + 2x + 3\)[/tex], is a polynomial. Thus, [tex]\(9x\)[/tex] is a factor of [tex]\(3x^3 + 18x^2 + 27x\)[/tex].

2. Testing [tex]\(x^3\)[/tex]:

Dividing [tex]\(3x^3 + 18x^2 + 27x\)[/tex] by [tex]\(x^3\)[/tex]:
[tex]\[ \frac{3x^3 + 18x^2 + 27x}{x^3} = \frac{3x^3}{x^3} + \frac{18x^2}{x^3} + \frac{27x}{x^3} = 3 + \frac{18}{x} + \frac{27}{x^2} \][/tex]
The result, [tex]\(3 + \frac{18}{x} + \frac{27}{x^2}\)[/tex], is not a polynomial because it contains negative powers of [tex]\(x\)[/tex]. Thus, [tex]\(x^3\)[/tex] is not a factor of [tex]\(3x^3 + 18x^2 + 27x\)[/tex].

3. Testing [tex]\(x+3\)[/tex]:

Dividing [tex]\(3x^3 + 18x^2 + 27x\)[/tex] by [tex]\(x+3\)[/tex]:
Using polynomial long division or factoring, we find:
[tex]\[ 3x^3 + 18x^2 + 27x = 3x(x+3)^2 \][/tex]
Therefore:
[tex]\[ 3x(x+3)^2 \div (x+3) = 3x(x+3) \][/tex]
The result, [tex]\(3x(x+3)\)[/tex], is a polynomial. Thus, [tex]\(x+3\)[/tex] is a factor of [tex]\(3x^3 + 18x^2 + 27x\)[/tex].

4. Testing [tex]\(x-3\)[/tex]:

Dividing [tex]\(3x^3 + 18x^2 + 27x\)[/tex] by [tex]\(x-3\)[/tex]:
Using polynomial long division or substitution method to check if [tex]\(x-3\)[/tex] is a factor:
[tex]\[ 3(3)^3 + 18(3)^2 + 27(3) = 3(27) + 18(9) + 27(3) = 81 + 162 + 81 = 324 \neq 0 \][/tex]
Since plugging [tex]\(x = 3\)[/tex] into the polynomial does not yield zero, [tex]\(x-3\)[/tex] is not a factor of [tex]\(3x^3 + 18x^2 + 27x\)[/tex].

In conclusion, the factors of the polynomial [tex]\(3x^3 + 18x^2 + 27x\)[/tex] from the given choices are:
[tex]\[ 9x \quad \text{and} \quad x+3 \][/tex]