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The graph of the function [tex]\( f(x) = -(x+6)(x+2) \)[/tex] is shown below.

Which statement about the function is true?

A. The function is increasing for all real values of [tex]\( x \)[/tex] where [tex]\( x \ \textless \ -4 \)[/tex].

B. The function is increasing for all real values of [tex]\( x \)[/tex] where [tex]\(-6 \ \textless \ x \ \textless \ -2\)[/tex].

C. The function is decreasing for all real values of [tex]\( x \)[/tex] where [tex]\( x \ \textless \ -6 \)[/tex] and where [tex]\( x \ \textgreater \ -2 \)[/tex].

D. The function is decreasing for all real values of [tex]\( x \)[/tex] where [tex]\( x \ \textless \ -4 \)[/tex].


Sagot :

To analyze the behavior of the function [tex]\( f(x) = -(x+6)(x+2) \)[/tex], we need to understand its properties, specifically where it increases and where it decreases.

1. Identify the roots: The given function is a quadratic function, which can be written in standard form as:
[tex]\[ f(x) = -(x+6)(x+2) \][/tex]

Expanding this, we get:
[tex]\[ f(x) = -(x^2 + 8x + 12) = -x^2 - 8x - 12 \][/tex]

The roots of the function are [tex]\( x = -6 \)[/tex] and [tex]\( x = -2 \)[/tex].

2. Vertex of the parabola: Since this is a quadratic function that opens downwards (the coefficient of [tex]\( x^2 \)[/tex] is negative), the vertex represents the maximum point. The x-coordinate of the vertex can be found using the midpoint of the roots:
[tex]\[ x_{\text{vertex}} = \frac{x_1 + x_2}{2} = \frac{-6 + (-2)}{2} = \frac{-8}{2} = -4 \][/tex]

3. Intervals of increase and decrease:
- For [tex]\( x < -4 \)[/tex], the function is decreasing because we are moving away from the vertex to the left.
- For [tex]\( x > -4 \)[/tex], the function is also decreasing because we are moving away from the vertex to the right.
- Specifically, the function will be increasing as we move towards the vertex from each side. Therefore, it increases on the interval [tex]\( -6 < x < -2 \)[/tex].

Given this analysis, the correct statement about the function is:
[tex]\[ \text{The function is increasing for all real values of } x \text{ where } -6 < x < -2. \][/tex]

Thus, the answer is:
The function is increasing for all real values of [tex]\( x \)[/tex] where [tex]\( -6 < x < -2 \)[/tex].