If 0 < x ≤ 1, then which one of the following is the maximum value of (x-1)2 +x ?
Point A is 10 km west of point B. Point B is 30 km north of point C. Point C is 20 km east of point D. What is the distance between point A and D?
There are 3 doors to a lecture room. In how many ways can a lecturer enter the room from one door and leave from another door ?