at our lessons we answer the teacher's questions.
in england they don't go to school every day.
i do my homework in my bedroom.
the pupils on duty tidy the classroom.
all the pupils have to wear uniforms.
i come to school at a quarter to eight.
we like to make reports.
i do me homework every day.
i have my music lessons two times a week.
we have english three times a week.
this magazine is published to times a month.
i visit my aunt three times a month.
i never miss classes.
i go to the forest very often.
they seldom go to the theatre.
i don't want to answer the teacher's questions.
my friends and i go to school every day.
i do my homework at school.
every friday the students tidy their classrooms.
we don't have to wear a uniform at our school.
as a rule they come to school at 8 a.m.
my sister like to make reports on geography.
we must do washing up every day.
i have to play chess two times a week.
we go to a swimming pool three times a week.
my mother goes to the dentist two times a month.
i go to the disco three times a month.
i have never been to volgograd.
she goes to the cinema very often.
they seldom sing and dance.
Есть одно разложение этих чисел на сто карточек
1-2, 3-4, 5-6, 197-198, 199-200 итого сто пар - других разложений нет , иначе бы не выполнялся пункт что разница на каждой карточке равна 1
Сумма на карточках 3 (1*4-1), 7 (2*4-1), 11 (3*4 -1), 395 (99*4-1), 399 (4*100-1) то есть можно вывести общую формулу 4*k-1 (k⊂[1 100])
Надо теперь определить сумма 21-ой карточки равно 2017 или нет
сложим 21 карточку
(4*k₁-1)+(4*k₂-1)+(4*k₃-1)+...+(4*k₂₀-1)+(4*k₂₁-1)=2017
4*(k₁+k₂+k₃+...+k₂₀+k₂₁)-21=2017
4*(k₁+k₂+k₃+...+k₂₀+k₂₁)=2038
k₁+k₂+k₃+...+k₂₀+k₂₁= 2038/4 = 509.5
не может быть , так как слева сумма натуральных чисел и сумма натуральное число, а справа дробь