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Which statement is true about the function [tex]f(x) = \sqrt{-x}[/tex]?

A. The domain of the graph is all real numbers.
B. The range of the graph is all real numbers.
C. The domain of the graph is all real numbers less than or equal to 0.
D. The range of the graph is all real numbers less than or equal to 0.


Sagot :

Let's analyze the function [tex]\( f(x) = \sqrt{-x} \)[/tex].

1. Domain:
- The function involves a square root, which requires its argument to be non-negative, because the square root of a negative number is not defined in the real number system.
- The argument inside the square root is [tex]\(-x\)[/tex]. Therefore, we need [tex]\(-x \geq 0\)[/tex].
- Solving this inequality, we get:
[tex]\[ -x \geq 0 \implies x \leq 0 \][/tex]
- Hence, the domain of the function is all real numbers less than or equal to 0.

2. Range:
- For the range, consider the values that [tex]\( f(x) \)[/tex] can take as [tex]\( x \)[/tex] varies over its domain.
- Since the square root function always returns non-negative values (i.e., the result is always greater than or equal to 0), we look at how [tex]\( f(x) = \sqrt{-x} \)[/tex] behaves:
- When [tex]\( x = 0 \)[/tex], [tex]\( f(0) = \sqrt{-0} = \sqrt{0} = 0 \)[/tex].
- As [tex]\( x \)[/tex] decreases (becomes more negative), [tex]\(-x\)[/tex] becomes more positive, and thus [tex]\( \sqrt{-x} \)[/tex] increases.
- Therefore, [tex]\( f(x) \)[/tex] will always produce values that are greater than or equal to 0.
- So, the range of [tex]\( f(x) \)[/tex] is all non-negative real numbers, i.e., [tex]\( [0, \infty) \)[/tex].

To summarize, among the given statements, the one that correctly describes the function [tex]\( f(x) = \sqrt{-x} \)[/tex] is:

The domain of the graph is all real numbers less than or equal to 0.

Thus, the correct statement is:

The domain of the graph is all real numbers less than or equal to 0.