Respuesta :
Prime polynomials cannot be factorized in smaller degree polynomials. The prime polynomials out of the considered option are:
- Option 1: x^2 + 9
- Option 3: x^2 + 3x + 9
What are prime polynomials?
Those polynomials with integer coefficients that cannot be factored further, with factors of lower degree and integer coefficients are called prime polynomial.
(it is necessary that no factors exists having their coefficients are still integers and they're of lower degree)
Checking all the options for them being prime or not:
- Option 1: [tex]x^2 + 9[/tex]
Take [tex](x+a)(x+b) = x^2 + 9[/tex]
Then, expanding it gives:
[tex]x^2 + (a+b)x + ab = x^2 + 9 \implies a+b = 0, ab = 9[/tex]
or we get: [tex]a = -b, ab = -b^2 = 9, b^2 = -9[/tex]
Square of a real number doesn't exist, so this factor doesn't exist. Thus, it is prime polynomial.
- Option 2: [tex]x^2 - 9[/tex]
We have the identity [tex](a+b)(a-b) = a^2 - b^2[/tex]
and since 9 is square of 3, therefore, we get:
[tex]x^2 -9 = x^2 -3^2 = (x+3)(x-3)[/tex]
So it got factorized. Thus, not a prime polynomial.
- Option 3: [tex]x^2 +3x + 9[/tex]
Take [tex](x+a)(x+b) = x^2 + 3x + 9[/tex]
Then, expanding it gives:
[tex]x^2 + (a+b)x + ab = x^2 + 3x + 9 \implies a+b = 3, ab = 9[/tex]
That gives:
[tex]a = 3-b\\ab = b(3-b) = 3b - b^2 = 9\\b^2 -3b + 9 = 0[/tex]
Solving this quadratic equation by root formula gives:
[tex]b = \dfrac{-(-3) \pm \sqrt{(-3)^2 -4(1)(9)} }{2}\\\\b = \dfrac{-(-3) \pm \sqrt{-27} }{2}\\[/tex]
this makes 'b' a complex number and it doesn't remain a real number as its expression contains square root of a negative number.
Thus, this polynomial cannot be factorized in terms of smaller degree polynomials. Thus, its a prime polynomial.
- Option 4: [tex]-2x^2 + 8[/tex]
Taking -2 common out, we get:
[tex]-2(x^2 - 4) = -2(x^2 - 2^2) = -2(x-2)(x+2)[/tex]
Thus, it got factorized, and therefore not a prime polynomial.
Thus, the prime polynomials out of the considered option are:
- Option 1: [tex]x^2 + 9[/tex]
- Option 3: [tex]x^2 + 3x + 9[/tex]
Learn more about prime polynomials here:
https://brainly.com/question/10717989
Answer:
A.x2 + 9
B.x2 + 3x + 9
Step-by-step explanation:
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