Водном месяце января ровно 4 вторника и 4 субботы.на какой день 1 января выпадает в этом году?

На пятницу, посмотрел в компютерном календаре

1  yesterday i had  breakfast at the canteen.  2  last summer we went to the black sea.  3  he didn't call  me last week.  4  why did this girl come to  our office yesterday?   5  when did  you buy tickets last time?   6  last june the boys played  football every morning.  7  on sunday my parents  were at the theatre.  8  i didn't take part at the conference last month.  9  he lived in kiev in his childhood.  10  where did  he send his message?   2 трансформируйте предложения в past simplе  1  he often played chess.  2  our classes began at 9 a. m.  3  she  was always busy.  4  what did you do in the evening?   5  my sister didn’t study at school, she worked at the hospital. 6  my friend prefered tea to coffee.  7  i found many stories in this magazine.  8  he was in my room,  wasn't he?   9  why did you always ask so many questions?   10  jasmine seldom visited her grandparents. 3 образуйте отрицательную форму предложений  1  in summer she didn't get up early.  2  mr. white  didn't write a lot of letters yesterday.  3  on friday they weren't at the station.  4  we didn't  enjoy our time in rome.  5  they didn't  watch a football match last weekend.  6  the girl didn't open a box at once.  7  i didn't leave my keys on the table.  8  the engineer didn't go on business trip on monday.  9  my friend didn't want to move to another flat.  10  i didn't find a surprise in the present-box. 4 поставьте вопросы к предложениям.  1  he learned english at school. (where? what language? why? or …? )  where did he learn english? what language did he learn? why did he learn english? did he learn english or french? 2  the train was five hours late. (what? why? )  what was 5 hours late? why was the train five hours late? 3  i was going to stay at my aunt’s in the crimea. (where? who? or …? ) where was i going to stay in the crimea? who was going to stay at the aunt's in the crimea? was i going to stay at my aunt's or in the hotel in the crimea?   4  they stayed in moscow only for two days. (why? where? how long? ) why did they stay in m only for 2 days? where did they stay? how long did they stay in m?   5  i bought a very beautiful dress in this shop last weekend. (where? what? when? ) where did i buy a very beautiful dress last weekend? what did i buy in this shop last weekend? when did i buy this beautiful dress in the shop? 6  they traveled to cyprus by sea. (how? where? or …? ) how did they travel to c? where did they travel to? did they travel to c or ibiza?   7  i didn’t find your telephone number. (what? why? )  what didn't i find? why didn't i find your telephone number? 8  in his childhood he was always a leader among his friends. (what? when? who? )  what was he in his childhood? when was he a leader among his friends? who was always a leader among his friends in his childhood? 9  he caught a cold last month. (what? when? why? ) what did he catch? when did he catch a cold? why did he catch a cold?   10  we did our lessons together. (what? how? ) what did we do together? how did we do our lessons?

В решении.

Объяснение:

Лодка спускается вниз по реке из пункта А в пункт В,  находящийся в 10 км от А, а затем возвращается в А. Если  собственная скорость лодки 3 км/ч, то путь из А в В занимает  на 2 ч 30 мин меньше, чем из В в А. Какой должна быть  собственная скорость лодки, чтобы поездка из А в В заняла 2  часа?

Формула движения: S=v*t

S - расстояние            v - скорость             t – время

2 часа 30 мин = 2,5 (часа).

Для ответа на вопрос задачи нужно сначала найти скорость течения реки.

х - скорость течения реки.

3 + х - скорость лодки по течению.

3 - х - скорость лодки против течения.

10/(3 + х) - время лодки по течению.

10/(3 - х) - время лодки против течения.

1) По условию задачи уравнение:

10/(3 - х) - 10/(3 + х) = 2,5

Умножить уравнение на (3 + х)(3 - х), чтобы избавиться от дробного выражения:

10*(3 + х) - 10*(3 - х) = 2,5*(9 - х²)

30 + 10х - 30 + 10х = 22,5 - 2,5х²

2,5х² + 20х - 22,5 = 0

Разделить уравнение на 2,5 для упрощения:

х² + 8х - 9 = 0, квадратное уравнение, ищем корни:

D=b²-4ac = 64 + 36 = 100         √D= 10

х₁=(-b-√D)/2a

х₁=(-8-10)/2 = -18/2 = -9, отбрасываем, как отрицательный.                

х₂=(-b+√D)/2a  

х₂=(-8+10)/2

х₂=2/2

х₂=1 (км/час) - скорость течения реки.

Проверка:

10/2 - 10/4 = 5 - 2,5 = 2,5 (часа), верно.

2) Какой должна быть  собственная скорость лодки, чтобы поездка из А в В заняла 2  часа?

х - собственная скорость лодки.

х + 1 - скорость лодки по течению.

10/(х + 1) - время лодки по течению.

По условию вопроса уравнение:

10/(х + 1) = 2

10 = 2(х + 1)

10 = 2х + 2

10 - 2 = 2х

2х = 8

х = 8/2

х = 4 (км/час) - такой должна быть  собственная скорость лодки, чтобы поездка из А в В заняла 2  часа.