Use a graphing calculator to graph the function [tex]f(x) = -\sqrt{x}[/tex]. Which list contains three points that lie on the graph of the function?

A. [tex]$(-9, 3), (-4, 2), (-1, 1)$[/tex]
B. [tex]$(1, 1), (4, 2), (9, 3)$[/tex]
C. [tex]$(-9, -3), (-4, -2), (-1, -1)$[/tex]
D. [tex]$(1, -1), (4, -2), (9, -3)$[/tex]



Answer :

To determine which set of points lies on the graph of the function [tex]\( f(x) = -\sqrt{x} \)[/tex], we will evaluate the function [tex]\( f(x) \)[/tex] at each [tex]\( x \)[/tex]-coordinate provided in the points and check if the calculated [tex]\( y \)[/tex]-value matches the [tex]\( y \)[/tex]-coordinate of the point.

First, let's understand the function [tex]\( f(x) = -\sqrt{x} \)[/tex]. This function only has real values for [tex]\( x \geq 0 \)[/tex], because the square root of a negative number is not a real number. The output of [tex]\( f(x) \)[/tex] is the negative of the square root of [tex]\( x \)[/tex].

We will proceed by checking each list of points:

### List 1: [tex]\((-9,3), (-4,2), (-1,1)\)[/tex]
1. For the point [tex]\((-9, 3)\)[/tex]:
[tex]\[ f(-9) = -\sqrt{-9} \quad \text{(not a real number)} \][/tex]
2. For the point [tex]\((-4, 2)\)[/tex]:
[tex]\[ f(-4) = -\sqrt{-4} \quad \text{(not a real number)} \][/tex]
3. For the point [tex]\((-1, 1)\)[/tex]:
[tex]\[ f(-1) = -\sqrt{-1} \quad \text{(not a real number)} \][/tex]

None of these points are on the graph because they involve the square root of negative numbers, which are not defined in the real number system.

### List 2: [tex]\((1,1), (4,2), (9,3)\)[/tex]
1. For the point [tex]\((1, 1)\)[/tex]:
[tex]\[ f(1) = -\sqrt{1} = -1 \quad \text{(not equal to 1)} \][/tex]
2. For the point [tex]\((4, 2)\)[/tex]:
[tex]\[ f(4) = -\sqrt{4} = -2 \quad \text{(not equal to 2)} \][/tex]
3. For the point [tex]\((9, 3)\)[/tex]:
[tex]\[ f(9) = -\sqrt{9} = -3 \quad \text{(not equal to 3)} \][/tex]

None of these points are on the graph because the calculated [tex]\( y \)[/tex]-values do not match the [tex]\( y \)[/tex]-coordinates of the points.

### List 3: [tex]\((-9,-3), (-4,-2), (-1,-1)\)[/tex]
1. For the point [tex]\((-9, -3)\)[/tex]:
[tex]\[ f(-9) = -\sqrt{-9} \quad \text{(not a real number)} \][/tex]
2. For the point [tex]\((-4, -2)\)[/tex]:
[tex]\[ f(-4) = -\sqrt{-4} \quad \text{(not a real number)} \][/tex]
3. For the point [tex]\((-1, -1)\)[/tex]:
[tex]\[ f(-1) = -\sqrt{-1} \quad \text{(not a real number)} \][/tex]

None of these points are on the graph for the same reasons as list 1.

### List 4: [tex]\((1,-1), (4,-2), (9,-3)\)[/tex]
1. For the point [tex]\((1, -1)\)[/tex]:
[tex]\[ f(1) = -\sqrt{1} = -1 \quad \text{(equal to -1)} \][/tex]
2. For the point [tex]\((4, -2)\)[/tex]:
[tex]\[ f(4) = -\sqrt{4} = -2 \quad \text{(equal to -2)} \][/tex]
3. For the point [tex]\((9, -3)\)[/tex]:
[tex]\[ f(9) = -\sqrt{9} = -3 \quad \text{(equal to -3)} \][/tex]

All of these points are on the graph because for each point, the [tex]\( y \)[/tex]-value is equal to [tex]\( -\sqrt{x} \)[/tex].

So, the list that contains three points that lie on the graph of the function [tex]\( f(x) = -\sqrt{x} \)[/tex] is:

[tex]\[ (1,-1), (4,-2), (9,-3) \][/tex]

Thus, the correct answer is the fourth list.

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