Which second-degree polynomial function has a leading coefficient of -1 and root 4 with multiplicity 2?

A. [tex]\( f(x) = -x^2 - 8x - 16 \)[/tex]
B. [tex]\( f(x) = -x^2 + 8x - 16 \)[/tex]
C. [tex]\( f(x) = -x^2 - 8x + 16 \)[/tex]
D. [tex]\( f(x) = -x^2 + 8x + 16 \)[/tex]



Answer :

To determine the second-degree polynomial function with a leading coefficient of -1 and a root 4 with multiplicity 2, we need to follow these steps:

1. Understand what a root with multiplicity means:
- A root [tex]\( r \)[/tex] with multiplicity [tex]\( m \)[/tex] means that the factor [tex]\( (x - r)^m \)[/tex] appears in the polynomial.
- In this case, the root is 4, and it has a multiplicity of 2. This implies the factor [tex]\( (x - 4)^2 \)[/tex].

2. Form the polynomial using the root and given multiplicity:
- The polynomial factor can be written as [tex]\( (x - 4)^2 \)[/tex].
- Since the polynomial has a leading coefficient of -1, we multiply the entire factor by -1.
- Thus, the polynomial function [tex]\( f(x) \)[/tex] would be [tex]\( -1 \times (x - 4)^2 \)[/tex].

3. Expand the polynomial:
- First, expand [tex]\( (x - 4)^2 \)[/tex]:
[tex]\[ (x - 4)^2 = x^2 - 8x + 16 \][/tex]
- Now multiply this by the leading coefficient -1:
[tex]\[ -1 \times (x^2 - 8x + 16) = -x^2 + 8x - 16 \][/tex]

4. Compare it to the given options:
- The expanded form yields the polynomial [tex]\( -x^2 + 8x - 16 \)[/tex].
- Compare this with the options provided:
[tex]\[ f(x) = -x^2 - 8x - 16 \\ f(x) = -x^2 + 8x - 16 \\ f(x) = -x^2 - 8x + 16 \\ f(x) = -x^2 + 8x + 16 \][/tex]

- The correct polynomial [tex]\( -x^2 + 8x - 16 \)[/tex] matches the second option.

Hence, the second-degree polynomial function with a leading coefficient of -1 and a root 4 with multiplicity 2 is:
[tex]\[ \boxed{f(x) = -x^2 + 8x - 16} \][/tex]

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