Select the correct answer.

Consider this absolute value function:
[tex]\[ f(x)=|x+3| \][/tex]

If function [tex]\( f \)[/tex] is written as a piecewise function, which piece will it include?

A. [tex]\( x+3, \ x \geq 3 \)[/tex]
B. [tex]\( x+3, \ x \geq -3 \)[/tex]
C. [tex]\( -x+3, \ x \ \textless \ -3 \)[/tex]
D. [tex]\( -x-3, \ x \ \textless \ 3 \)[/tex]



Answer :

To transform the given absolute value function [tex]\( f(x) = |x + 3| \)[/tex] into a piecewise function, we need to consider how the absolute value affects the expression within it.

The absolute value function [tex]\( |a| \)[/tex] is defined as:

[tex]\[ |a| = \begin{cases} a & \text{if } a \geq 0, \\ -a & \text{if } a < 0. \end{cases} \][/tex]

Applying this definition to [tex]\( f(x) = |x + 3| \)[/tex]:

[tex]\[ f(x) = |x + 3| = \begin{cases} x + 3 & \text{if } x + 3 \geq 0, \\ -(x + 3) & \text{if } x + 3 < 0. \end{cases} \][/tex]

Now we can solve the conditions for [tex]\( x \)[/tex]:

1. For [tex]\( x + 3 \geq 0 \)[/tex]:
[tex]\[ x + 3 \geq 0 \implies x \geq -3 \][/tex]
Therefore:
[tex]\[ f(x) = x + 3 \text{ for } x \geq -3 \][/tex]

2. For [tex]\( x + 3 < 0 \)[/tex]:
[tex]\[ x + 3 < 0 \implies x < -3 \][/tex]
Therefore:
[tex]\[ f(x) = -(x + 3) = -x - 3 \text{ for } x < -3 \][/tex]

So the piecewise function can be written as:

[tex]\[ f(x) = \begin{cases} x + 3 & \text{if } x \geq -3, \\ -x - 3 & \text{if } x < -3. \end{cases} \][/tex]

From the given multiple-choice options, we can identify the correct piece:

A. [tex]\( x+3, x \geq 3 \)[/tex] – This is incorrect because it does not cover the correct domain for when [tex]\( x \geq -3 \)[/tex].

B. [tex]\( x + 3, x \geq -3 \)[/tex] – This is correct because it matches our piecewise condition for [tex]\( x \geq -3 \)[/tex].

C. [tex]\( -x + 3, x < -3 \)[/tex] – This is incorrect because the correct expression for [tex]\( x < -3 \)[/tex] is [tex]\( -x - 3\)[/tex].

D. [tex]\( -x - 3, x < 3 \)[/tex] – This is incorrect because it does not match the condition [tex]\( x < -3 \)[/tex] and misrepresents the function [tex]\( -x - 3 \)[/tex].

Therefore, the correct answer is:

B. [tex]\( x + 3, x \geq -3 \)[/tex]