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Which best describes the range of the function [tex]f(x) = 2(3)^x[/tex]?

A. [tex]y \ \textgreater \ 0[/tex]
B. [tex]y \geq 0[/tex]
C. [tex]y \ \textgreater \ 2[/tex]
D. [tex]y \geq 2[/tex]


Sagot :

To determine the range of the function [tex]\( f(x) = 2 \cdot 3^x \)[/tex], let's analyze its behavior.

1. Understanding the Function:
- [tex]\( f(x) = 2 \cdot 3^x \)[/tex] is an exponential function where the base of the exponent, 3, is greater than 1.
- The coefficient 2 is a positive constant that scales the exponential function.

2. Behavior of Exponential Functions:
- For [tex]\( 3^x \)[/tex], where [tex]\( 3 \)[/tex] is the base, as [tex]\( x \)[/tex] increases, [tex]\( 3^x \)[/tex] grows rapidly.
- As [tex]\( x \)[/tex] decreases (negative values), [tex]\( 3^x \)[/tex] approaches 0 but never becomes 0. It gets very close to 0.

3. Impact of the Coefficient 2:
- The overall function [tex]\( f(x) = 2 \cdot 3^x \)[/tex] scales the values of [tex]\( 3^x \)[/tex] by a factor of 2.
- Therefore, as [tex]\( x \)[/tex] increases, [tex]\( 2 \cdot 3^x \)[/tex] grows very rapidly.
- As [tex]\( x \)[/tex] decreases, [tex]\( 2 \cdot 3^x \)[/tex] gets close to 0 but always remains positive (since 2 times a positive number is still positive).

4. Evaluating the Range:
- For very large negative [tex]\( x \)[/tex]: [tex]\( f(x) = 2 \cdot 3^x \)[/tex] approaches 2 times a very small positive number (close to zero).
- For very large positive [tex]\( x \)[/tex]: [tex]\( f(x) = 2 \cdot 3^x \)[/tex] approaches very large positive values.

Thus, the function [tex]\( f(x) = 2 \cdot 3^x \)[/tex] always results in a positive output and never touches 0. Therefore, the best description of the range of [tex]\( f(x) = 2 \cdot 3^x \)[/tex] is:
[tex]\[ y > 0 \][/tex]