Is the whole real set. This means that the domain is :
domf=(-∞,∞)
This comes from the fact that the functions is a polynomial. Nevertheless, given that x represents the number of people, in the context of the problem the domain has to be :
he would have traveled 210 miles because in half an hour he would have traveled 30 miles and in 3 hours he would have traveled 180 miles. so we have to add those up and we get our answer: 210 miles
