I actually have three but i put them up one at a time.

The first:

A truck is 250 mi due east of a sports car and is traveling west at a constant speed of 60mi/h. Meanwhile, the sports car is going north at 80mi/h. When will the truck and the car be closest to each other? what is the minimum distance between them? Hint: Minimize the square of the distance. The answer says The minimum distance is 200 mi.

I figure this is a Pythag. theorem problem. the adjacent(the truck) is heading left at 60mi/h. The opposite(the car) is going up at 80mi/h. and hypot. is 250mi. I tried deriving to get x or y, but that did not work. Please help.