The parent function, , has a domain of or , because the value under the radical cannot be less than 0 (we cannot take the square root of a negative number). Thus, by setting everything<em></em><em>inside</em> the radical to 0, we can find the domain of this function:
If Teresa drove 936 miles in 13 hours, this would mean she would have driven 72 miles every hour. 72 times 9 equals 648. After 9 hours, she would have driven 648 miles.