Consider the graph of the function [tex]\( f(x) = 2^x \)[/tex].

Which statement describes a key feature of the function [tex]\( g \)[/tex] if [tex]\( g(x) = 2 f(x) \)[/tex]?

A. horizontal asymptote of [tex]\( y = 2 \)[/tex]

B. [tex]\( y \)[/tex]-intercept at [tex]\( (0, 2) \)[/tex]

C. horizontal asymptote of [tex]\( y = -2 \)[/tex]

D. [tex]\( y \)[/tex]-intercept at [tex]\( (2, 0) \)[/tex]



Answer :

To solve the problem, consider the function [tex]\( f(x) = 2^x \)[/tex] and the modified function [tex]\( g(x) = 2 f(x) \)[/tex], which simplifies to [tex]\( g(x) = 2 \cdot 2^x \)[/tex].

First, let's analyze the graph and characteristics of [tex]\( f(x) = 2^x \)[/tex]:
1. The y-intercept occurs where [tex]\( x = 0 \)[/tex]:
[tex]\[ f(0) = 2^0 = 1 \][/tex]
Therefore, the y-intercept of [tex]\( f(x) \)[/tex] is at [tex]\( (0, 1) \)[/tex].

2. Since [tex]\( f(x) = 2^x \)[/tex] is an exponential function, it has a horizontal asymptote at [tex]\( y = 0 \)[/tex] as [tex]\( x \to -\infty \)[/tex].

Now, let's consider the modifications made for [tex]\( g(x) \)[/tex]:
[tex]\[ g(x) = 2 f(x) = 2 \cdot 2^x = 2^{x+1} \][/tex]

1. To find the y-intercept of [tex]\( g(x) \)[/tex]:
[tex]\[ g(0) = 2 \cdot 2^0 = 2 \cdot 1 = 2 \][/tex]
This means the y-intercept of [tex]\( g(x) \)[/tex] is at [tex]\( (0, 2) \)[/tex].

2. [tex]\( g(x) \)[/tex] is still an exponential function, and it will not change the horizontal asymptote from [tex]\( y = 0 \)[/tex] since the horizontal asymptote of the exponential function [tex]\( 2^x \)[/tex] is [tex]\( y = 0 \)[/tex] and this property remains unchanged under scaling by a constant factor.

Given these points:
- The y-intercept of [tex]\( g(x) \)[/tex] is [tex]\((0, 2)\)[/tex].

Therefore, the correct answer is:
[tex]\[ \text{B. } y\text{-intercept at } (0, 2) \][/tex]

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