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What are the domain and range of [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex]?

A. The domain is all real numbers. The range is all real numbers.
B. The domain is all real numbers. The range is all real numbers greater than zero.
C. The domain is all real numbers greater than zero. The range is all real numbers.
D. The domain is all real numbers greater than zero. The range is all real numbers greater than zero.


Sagot :

Let's analyze the function [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex].

### Domain:
The domain of a function is the set of all possible input values (x-values) for which the function is defined. In this case, [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex] is an exponential function. Exponential functions are defined for all real numbers, meaning you can input any real number for [tex]\( x \)[/tex] and the function will still produce a valid output.

So, the domain of [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex] is all real numbers.

### Range:
The range of a function is the set of all possible output values (y-values) the function can produce.

For [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex]:
- As [tex]\( x \to \infty \)[/tex] (x becomes very large), [tex]\( \left(\frac{1}{5}\right)^x \)[/tex] approaches 0 but never actually reaches 0. It remains positive no matter how large [tex]\( x \)[/tex] gets.
- As [tex]\( x \to -\infty \)[/tex] (x becomes very small), [tex]\( \left(\frac{1}{5}\right)^x \)[/tex] increases without bound because the base [tex]\( \frac{1}{5} \)[/tex] raised to a large negative power becomes a very large positive number.

Hence, the output values (y-values) of the function [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex] are always positive and can be any positive real number but never zero or negative.

So, the range of [tex]\( f(x) = \left(\frac{1}{5}\right)^x \)[/tex] is all real numbers greater than zero.

### Conclusion:
- The domain is all real numbers.
- The range is all real numbers greater than zero.

Therefore, the correct answer is:

The domain is all real numbers. The range is all real numbers greater than zero.