Step-by-step explanation:
we are calculating miles.
when we have speed, which is mph or miles/hour. what do we have to multiply it with to get miles ? hours !
miles/hour × hour = miles
so, in the function D(x) the speed 60 mph has to be multiplied by the hours spent driving to get the driven miles.
x = hours spent driving
the domain is the interval or set of all valid x (input) values. the range is the interval or set of all valid y (function result) values.
so what are valid x (number of driving hours) values ?
it starts with 0, if course (before actually driving). and it goes up to 4 (after 4 hours the 240 miles are "done").
the domain is
0 <= x <= 4
and the range ? that is all the function result values for the valid x values.
for x = 0 this starts at 240.
and goes down for x = 4 to 0.
the range is
0 <= y (= D(x)) <= 240
