Complete the expression so it forms a perfect-square trinomial. x² - 5x

The authors use the word “backbone” in lines 3 and 39 to indicate that

The different forms of a gene for a given trait are called .

17 a tourist was planning a trip by car for travelling at some constant speed for 2.5 hours. however, he found that if he increases the speed by 20 km/h he can cover the same distance in 30 minutes less time than it was planned. what was the planned speed of the tourist, in km/h?