Решить уравнение: х(х- 5) = 2 - 4х

1. you need to take a taxi if you want to catch the train. 2. children should not play with matches. 3. we should talk about this tomorrow. 4. that morning i had to go to the bank and so i was late for work. 5. he didn't have to get up early, it was a vacation 6, you should get off at the next stop 7. they are obliged to help you in this situation. 8. they had to wait long for the train? 9. you don't have to speak russian at the lessons of english. 10. we had to stay home yesterday because there was heavy rain, 11. they don't have to come here every day 12. students will be expected to stay after school 13. we need to prepare the reports to the next lesson? yes. 14. when he will have to answer all the letters? 15. adult children should care for their parents. 16. you had to stay late after work, isn't it?

Пусть x км/ч  - скорость велосипедиста, тогда скорость мотоциклиста (x+10) км/ч . время, за которое велосипедист проедет весь путь = 120/x часов, а мотоциклист за 120/(x+10)  часов. составляем уравнение: 120/x - 120/(x+10) = 6  |*x(x+10) 120(x+10) - 120x = 6x(x+10) 120x + 1200 - 120x = 6x^2 + 60x -6x^2 - 60x + 1200 = 0 -x^2 - 10x + 200 = 0 d = 100 + 800 = 900 = 30^2 x1 = (10 + 30)/-2 = - 20    - исключаем, т.к. скорость не может быть отрицательной x2 = (10-30)/ -2 = 10 км/ч - скорость велосипедиста скорость мотоциклиста = x + 10 = 10 + 10 = 20 км/ч ответ: 20