6.( ) Велосипедист был в пути 4 часа. За первый час он проехал х км, а в каждый следующий час проезжал на 1 км больше, чем в предыдущий. Найдите путь, который проехал велосипедист: 1) за второй час; 2) за третий час;
3) за первые два часа; 4) за все время решите
а) Пусть скорость второго поезда -х км/ч, расстояние он пройдет за 120/х часов.
Тогда скорость первого поезда (х+12) км/ч, то же расстояние он пройдет за 120/х+12 часов.
Первый поезд проходит это расстояние на 50 мин = 5/6 часа быстрее, чем второй. Составляем уравнение:
120/х-120/х+12=5/6
делим обе части на 120
1/х-1/х+12=1/(6*24)
(х+12-х)/х(х+12)=1/144
12/х(х+12)=1/144
х(х+12)=12*144
х^2 + 12х -1728=0
D=b^2-4ac=12^2-4*1* (-1728)=144+6912=7056
корень из дискриминанта =84
х1=(-12+84)/2=36 км/ч
х2=(-12-84)/2=-48 (не подходит по условиям, т.к. скорость не может быть отрицательной)
36+12=48 км/ч
ответ: 36 км/ч и 48 км/ч
б)Пусть х км/ч - скорость велосипедиста, тогда (х+12) км/ч - скорость мотоциклиста
Мотоциклист проходит расстояние на 2 часа 40мин=2 2/3ч быстрее велосипедиста. Расстояние между селами 64 км. Составим уравнение:
64/х - 64/(х+12) = 8/3
192х+2304-192х=8х2+96х
8х²+96х-2304=0
х²+12х-288=0
D=12^2-4*1*(-288)=144+1152=1296
корень из дискриминанта = 36
х1=(-12-36)/2=-24 (не подходит по условиям задачи)
х=(-12+36):2 =12км/ч - скорость велосипедиста
12+12=24км/ч - скорость мотоциклиста
ответ: 12 км/ч и 24 км/ч
Every season has its own charm and is good in its own way. My city is situated in
southern part of Kazakhstan and we have four seasons here: winter, spring, summer and
autumn
My favorite one is summer. Summer is the hottest season in the year. It begins in June
and ends in August. In summer the sky is clear and cloudless. The days are long and the
nights are short and warm. When it is hot I can swim in a nearby river. I like to swim, lie
in the sun, and play outdoors in summer. The weather is usually fine. Sometimes it rains.
But the rains are usually warm.
Autumn comes after summer. It brings heavy rains and winds to our region. Honestly, I
don't like autumn. The days are becoming shorter, the sun loses its force. It often rains. It
is the season of harvesting. It's muddy and gloomy outside. But it's a tasty and beautiful
season. Because there are a lot of fruits in autumn: apples, pears, grapes, plums. The
leaves are red, green and yellow and they fall down from the trees.
Winters are mild here. The first snow falls at the beginning of December. It quickly
melts though. It is getting colder day by day. The sun shines rarely but everything looks
so pretty covered with snow. My friends and I go skiing, sledding or snowballing on such
days.
Spring starts with sunshine and warm winds. The snow starts melting the birds start
singing their charming songs, trees start blooming, and there are lots of tulips and poppies
around.
I think all seasons are beautiful.
Mark the sentences True or False.
1) The days are long and the nights are short in autumn
2) I Like play indoors in summer
3) Sometimes the rains are usually cool in summer
4) It's muddy and gloomy outside in spring
5)There are a lot of tulips and poppies in Kazakhstan
Writing
Task.2 Complete the sentences. Use: Must, bave to, can't
1) You take a tent. a sleeping bag and a whistle with you
2) You
cook at a campsite
3) You
take a first-aid kit with you
4) You clean around a tent
5) Jake isn't happy because they light the campfire