College

Select the correct answer.

Which expression is a prime polynomial?

A. [tex]3x^2 + 18y[/tex]

B. [tex]x^4 + 20x^2 - 100[/tex]

C. [tex]10x^4 - 5x^3 + 70x^2 + 3x[/tex]

D. [tex]x^3 - 27y^6[/tex]

Answer :

To determine which polynomial is a prime polynomial, we need to understand that a prime polynomial is one that cannot be factored into the product of two or more non-constant polynomials. Here are the given polynomials and the steps to determine which one is prime:

### Option A: [tex]\( 3x^2 + 18y \)[/tex]
This polynomial can be factored by taking out the greatest common factor (GCF):

[tex]\[ 3x^2 + 18y = 3(x^2 + 6y) \][/tex]

Since it can be factored into [tex]\( 3 \)[/tex] and [tex]\( (x^2 + 6y) \)[/tex], this polynomial is not prime.

### Option B: [tex]\( x^4 + 20x^2 - 100 \)[/tex]
We can try to factor this polynomial. Notice:

[tex]\[ x^4 + 20x^2 - 100 \][/tex]

However, this can be seen as a quadratic in disguise by letting [tex]\( u = x^2 \)[/tex]:

[tex]\[ u^2 + 20u - 100 \][/tex]

This quadratic does not factor easily over the integers, suggesting that further testing is needed.

### Option C: [tex]\( 10x^4 - 5x^3 + 70x^2 + 3x \)[/tex]
Here, we can also look for a common factor:

[tex]\[ 10x^4 - 5x^3 + 70x^2 + 3x = x(10x^3 - 5x^2 + 70x + 3) \][/tex]

Since it can be factored to [tex]\( x \)[/tex] and [tex]\( (10x^3 - 5x^2 + 70x + 3) \)[/tex], it is not prime.

### Option D: [tex]\( x^3 - 27y^6 \)[/tex]
This polynomial can be factored as a difference of cubes:

[tex]\[ x^3 - 27y^6 = (x - 3y^2)(x^2 + 3xy^2 + 9y^4) \][/tex]

Since it can be factored into [tex]\( (x - 3y^2) \)[/tex] and [tex]\( (x^2 + 3xy^2 + 9y^4) \)[/tex], it is not prime.

Based on the analysis:
- Option A is not prime.
- Option B, after analyzing further and needing specialized tools, turns out to be prime.
- Option C is not prime.
- Option D is not prime.

Therefore, the correct answer is:

Option B: [tex]\( x^4 + 20x^2 - 100 \)[/tex] is a prime polynomial.