Answer:
a) d(t) = 360 - 60t
Step-by-step explanation:
In this problem, the initial distance between Joe and Dallas is
d0 = 360 miles
Later, Joe travels at a speed of 60 miles/hour.
This means that the distance covered by Joe in a time t is
x(t) = 60t
where t is the time measured in hours.
However, Joe is moving towards Dallas: this means that the distance from Dallas is decreasing as time increases, therefore the distance is decreasing at a rate of
-60t
And therefore, the final expression of Joe's distance from Dallas is
d(t) = 360 - 60t
In fact, we notice that at t = 0, the distance from Dallas is 360 miles.
