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What are the domain and range of [tex]f(x) = \log (x-1) + 2[/tex]?

A. Domain: [tex]x \ \textgreater \ 1[/tex]; Range: [tex]y \ \textgreater \ 2[/tex]
B. Domain: [tex]x \ \textgreater \ 1[/tex]; Range: all real numbers
C. Domain: all real numbers; Range: [tex]y \ \textgreater \ 1[/tex]
D. Domain: all real numbers; Range: all real numbers

Sagot :

To determine the domain and range of the function [tex]\( f(x) = \log(x - 1) + 2 \)[/tex], we need to carefully analyze the behavior of the logarithmic function [tex]\( \log(x - 1) \)[/tex] and how it is affected by the addition of 2.

Step-by-Step Analysis:

1. Domain:
- The argument of the logarithm [tex]\( x - 1 \)[/tex] must be greater than 0 for the logarithm to be defined.
- Therefore, [tex]\( x - 1 > 0 \implies x > 1 \)[/tex].
- This means the domain of [tex]\( f(x) \)[/tex] is [tex]\( x > 1 \)[/tex].

2. Range:
- The logarithmic function [tex]\( \log(x - 1) \)[/tex] can take any real number value.
- So, [tex]\( \log(x - 1) \)[/tex] can be any real number from [tex]\( -\infty \)[/tex] to [tex]\( \infty \)[/tex].
- When we add 2 to [tex]\( \log(x - 1) \)[/tex], we are shifting the entire set of values of [tex]\( \log(x - 1) \)[/tex] up by 2 units.
- Thus, the range of [tex]\( f(x) = \log(x - 1) + 2 \)[/tex] will be all real numbers greater than 2.

Conclusion:

- The domain of [tex]\( f(x) \)[/tex] is [tex]\( x > 1 \)[/tex].
- The range of [tex]\( f(x) \)[/tex] is [tex]\( y > 2 \)[/tex].

Therefore, the correct answer is:

[tex]\[ \text{Domain: } x > 1; \text{ Range: } y > 2 \][/tex]