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Which function's range includes -4?

A. [tex]y=\sqrt{x}-5[/tex]
B. [tex]y=\sqrt{x}+5[/tex]
C. [tex]y=\sqrt{x+5}[/tex]
D. [tex]y=\sqrt{x-5}[/tex]


Sagot :

Let's analyze each of the given functions step-by-step to determine if their range includes -4:

1. Function: [tex]\( y = \sqrt{x} - 5 \)[/tex]

To check if -4 is in the range:
[tex]\[ \begin{aligned} y = -4 & \implies -4 = \sqrt{x} - 5 \\ \implies -4 + 5 & = \sqrt{x} \\ \implies 1 & = \sqrt{x} \\ \implies x & = 1 \end{aligned} \][/tex]
Since [tex]\( x = 1 \)[/tex] is a valid solution (and [tex]\( x \)[/tex] must be non-negative as it is under a square root), -4 is in the range of [tex]\( y = \sqrt{x} - 5 \)[/tex].

2. Function: [tex]\( y = \sqrt{x} + 5 \)[/tex]

To check if -4 is in the range:
[tex]\[ \begin{aligned} y = -4 & \implies -4 = \sqrt{x} + 5 \\ \implies -4 - 5 & = \sqrt{x} \\ \implies -9 & = \sqrt{x} \end{aligned} \][/tex]
Since the square root of a number cannot be negative, -4 is not in the range of [tex]\( y = \sqrt{x} + 5 \)[/tex].

3. Function: [tex]\( y = \sqrt{x + 5} \)[/tex]

To check if -4 is in the range:
[tex]\[ \begin{aligned} y = -4 & \implies -4 = \sqrt{x + 5} \end{aligned} \][/tex]
The square root function [tex]\(\sqrt{\cdot}\)[/tex] only produces non-negative values. Therefore, [tex]\(-4\)[/tex] cannot be the output of a square root function. Consequently, -4 is not in the range of [tex]\( y = \sqrt{x + 5} \)[/tex].

4. Function: [tex]\( y = \sqrt{x - 5} \)[/tex]

To check if -4 is in the range:
[tex]\[ \begin{aligned} y = -4 & \implies -4 = \sqrt{x - 5} \end{aligned} \][/tex]
Similar to the previous case, the square root function [tex]\(\sqrt{\cdot}\)[/tex] only produces non-negative values. Therefore, [tex]\(-4\)[/tex] cannot be the output of a square root function. Thus -4 is not in the range of [tex]\( y = \sqrt{x - 5} \)[/tex].

In conclusion, the range of the function [tex]\( y = \sqrt{x} - 5 \)[/tex] includes -4.