kinds of rest are different. most often the choice of the rest depends on the person , from his character , as well as from the mood of the person.of course , we choose the kind of recreation ,proceeding from the situation , such as : weather , location. therefore, it does not always work combine what i would like to.a very popular form of recreation in the weekends are sports games (badminton, basketball, volleyball, football, tennis, hockey, they have a broad influence on the organism of the students. the most effective long and active rest is sports tourism-participation in sports activities.during tourist trips improves mood, there arises a burst of energy and strength. all this has a positive effect on the nervous system. in addition, the prolonged stay in the fresh air, especially when hiking with a lodging for the night under the open sky and in the tents, and contributes to tempering of the organism.
пусть скорость горной реки х плот плывет по реке 21 км в течение 21: х часов
туристы на лодке все расстояние проплыли за такое же время: 54: (12+х) плыла лодка по реке+ 6: 12по озеру и все это равно времени, за которое плот плывет по реке 21 км, =21: хсоставим и решим уравнение: 54: (12+х) +0,5 =21: хумножим обе части на х(12+х), чтобы избавиться от дробей: 54х +0,5х(12+х) =21(12+х)54х +6х +0,5х² =252+21х 0,5х²+39х -252=0d=b²-4ac=39²-4·0.5·-252=2025так как дискриминант больше нуля, то уравнение имеет два корняодин отрицательный и не подходит ( -84)
второй = 6 скорость течения горной реки 6 км/ч