Answer:
[tex]D(t)=-24t+166[/tex]
Step-by-step explanation:
Let
D(t) = the distance to the safe zone (measured in meters)
t = time (measured in seconds)
Given:
Rachel's rate = 24 meters per second
At [tex]t_1=4[/tex] seconds [tex]D(t_1)=70[/tex] meters
Find: D(t)
Rachel's rate is the slope of the function D(t). Since the distance is decreasing when the time is increasing, the slope must be negative.
Hence, the function expression is
[tex]D(t)=-24t+b[/tex]
To find b, substitute [tex]t_1=4[/tex] and [tex]D(t_1)=70:[/tex]
[tex]70=-24\cdot 4+b\\ \\70=-96+b\\ \\b=70+96\\ \\b=166[/tex]
So,
[tex]D(t)=-24t+166[/tex]