If a polynomial function [tex]\( f(x) \)[/tex] has roots [tex]\( 3+\sqrt{5} \)[/tex] and [tex]\( -6 \)[/tex], what must be a factor of [tex]\( f(x) \)[/tex]?

A. [tex]\( (x - (3 - \sqrt{5})) \)[/tex]
B. [tex]\( (x - (3 + \sqrt{5})) \)[/tex]
C. [tex]\( (x - (5 + \sqrt{3})) \)[/tex]
D. [tex]\( (x - (5 - \sqrt{3})) \)[/tex]



Answer :

To determine a factor of the polynomial function [tex]\( f(x) \)[/tex] given its roots, we need to consider the properties of polynomial roots.

Given roots are [tex]\( 3 + \sqrt{5} \)[/tex] and [tex]\(-6 \)[/tex].

First, note that for any polynomial with real coefficients, if [tex]\( 3 + \sqrt{5} \)[/tex] is a root, its conjugate [tex]\( 3 - \sqrt{5} \)[/tex] must also be a root. This is because roots involving square roots must come in conjugate pairs to ensure that the polynomial has real coefficients.

Therefore, the roots of the polynomial function [tex]\( f(x) \)[/tex] we have are:
1. [tex]\( 3 + \sqrt{5} \)[/tex]
2. [tex]\( 3 - \sqrt{5} \)[/tex] (conjugate)
3. [tex]\(-6\)[/tex]

Each of these roots corresponds to a factor of the polynomial. The factor corresponding to the root [tex]\( 3 + \sqrt{5} \)[/tex] is [tex]\((x - (3 + \sqrt{5}))\)[/tex].

Similarly, the factor corresponding to the root [tex]\( 3 - \sqrt{5} \)[/tex] is [tex]\((x - (3 - \sqrt{5}))\)[/tex].

Hence, one of the factors of [tex]\( f(x) \)[/tex] must be [tex]\((x - (3 - \sqrt{5}))\)[/tex].

Given the options:
1. [tex]\((x + (3 - \sqrt{5}))\)[/tex]
2. [tex]\((x - (3 - \sqrt{5}))\)[/tex]
3. [tex]\((x + (5 + \sqrt{3}))\)[/tex]
4. [tex]\((x - (5 - \sqrt{3}))\)[/tex]

The correct answer is:
[tex]\[ (x - (3 - \sqrt{5})) \][/tex]