High School

24. The function [tex]f[/tex] is given by [tex]f(x) = 3 \cdot 2^{(3-x)}[/tex]. The function [tex]f[/tex] can also be expressed as which of the following?

A. [tex]\frac{3}{8} \cdot \left(\frac{1}{2}\right)^x[/tex]
B. [tex]3 \cdot \left(\frac{1}{8}\right)^x[/tex]
C. [tex]24 \cdot \left(\frac{1}{2}\right)^x[/tex]
D. [tex]-216^x[/tex]

Answer :

We start with the function

[tex]$$
f(x)=3\cdot2^{(3-x)}.
$$[/tex]

Our first step is to rewrite the expression using properties of exponents. Notice that

[tex]$$
2^{(3-x)} = 2^3 \cdot 2^{-x}.
$$[/tex]

So, we have

[tex]$$
f(x) = 3\cdot2^3\cdot2^{-x}.
$$[/tex]

Since [tex]$2^3=8$[/tex], multiplying [tex]$3$[/tex] by [tex]$8$[/tex] gives

[tex]$$
3\cdot8=24.
$$[/tex]

Thus, the function becomes

[tex]$$
f(x)=24\cdot2^{-x}.
$$[/tex]

Recall that [tex]$2^{-x}$[/tex] can be written as [tex]$\left(\frac{1}{2}\right)^x$[/tex]. Therefore, we obtain

[tex]$$
f(x)=24\cdot\left(\frac{1}{2}\right)^x.
$$[/tex]

Thus, the equivalent expression for the function [tex]$f(x)$[/tex] is

[tex]$$
24 \cdot \left(\frac{1}{2}\right)^x.
$$[/tex]

This corresponds to option (b).