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The function [tex]\(D(t)\)[/tex] defines a traveler's distance from home, in miles, as a function of time, in hours.

[tex]\[ D(t) = \left\{ \begin{array}{cl}
300t + 125, & 0 \leq t \ \textless \ 2.5 \\
875, & 2.5 \leq t \leq 3.5 \\
75t + 612.5, & 3.5 \ \textless \ t \leq 6
\end{array} \right. \][/tex]

Which times and distances are represented by the function? Select three options:

A. The starting distance, at 0 hours, is 300 miles.
B. At 2 hours, the traveler is 725 miles from home.
C. At 2.5 hours, the traveler is still moving farther from home.
D. At 3 hours, the distance is constant, at 875 miles.
E. The total distance from home after 6 hours is [tex]\(1,062.5\)[/tex] miles.


Sagot :

Here's how we find the distances at the specified times using the piecewise function [tex]\( D(t) \)[/tex].

1. Starting distance (at [tex]\( t = 0 \)[/tex] hours):
The function at [tex]\( t = 0 \)[/tex] is given by:
[tex]\[ D(0) = 300(0) + 125 = 125 \text{ miles} \][/tex]
So, the starting distance is 125 miles.

2. Distance at [tex]\( t = 2 \)[/tex] hours:
For [tex]\( 0 \leq t < 2.5 \)[/tex], the distance function is [tex]\( D(t) = 300t + 125 \)[/tex]. Thus, at [tex]\( t = 2 \)[/tex]:
[tex]\[ D(2) = 300(2) + 125 = 600 + 125 = 725 \text{ miles} \][/tex]
So, at 2 hours, the traveler is 725 miles from home.

3. Distance at [tex]\( t = 2.5 \)[/tex] hours:
For [tex]\( 2.5 \leq t \leq 3.5 \)[/tex], the distance function is [tex]\( D(t) = 875 \)[/tex]. Thus, at [tex]\( t = 2.5 \)[/tex]:
[tex]\[ D(2.5) = 875 \text{ miles} \][/tex]
So, the traveler is not moving farther but has reached a constant distance of 875 miles at 2.5 hours.

4. Distance at [tex]\( t = 3 \)[/tex] hours:
For [tex]\( 2.5 \leq t \leq 3.5 \)[/tex], the distance function remains [tex]\( D(t) = 875 \)[/tex]. Thus, at [tex]\( t = 3 \)[/tex]:
[tex]\[ D(3) = 875 \text{ miles} \][/tex]
So, the traveler's distance is constant at 875 miles at 3 hours.

5. Total distance from home after [tex]\( t = 6 \)[/tex] hours:
For [tex]\( 3.5 < t \leq 6 \)[/tex], the distance function is [tex]\( D(t) = 75t + 612.5 \)[/tex]. Thus, at [tex]\( t = 6 \)[/tex]:
[tex]\[ D(6) = 75(6) + 612.5 = 450 + 612.5 = 1062.5 \text{ miles} \][/tex]
So, the total distance from home after 6 hours is 1062.5 miles.

Based on these calculations, the correct options are:
- At 2 hours, the traveler is 725 miles from home.
- At 3 hours, the distance is constant, at 875 miles.
- The total distance from home after 6 hours is 1062.5 miles.
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