Если у функции есть наименьшее значение, то она ограничена снизу. Сверху же она может быть как ограниченной, так и не ограниченной. Примеры: y=x² - ограничена снизу, но не ограничена сверху, y=sin(x) - ограничена и сверху. и снизу.
Sn= a1+an/2 *n
801=2+87/2 *n
n=18
an=a1+(n-1)d
87=2+17d
d=5
2)
S=(2a1+d(n-1))/2*n=(a1+an)/2*n
210=(a1+21)*7
a1+21=30
a1=9
an=a1+d(n-1)
21=9+d*6
21-9=d*6
d=2
1.
180-42=138
138÷2=69° меньший угол вертикального угла
69+42=111° больший угол вертикального угла
2.
180 = 4х
х=45° Меньший смежн угол
3х=135° больший смежн угол
1. You need to take a taxi if you want to catch a train.
2. Children should not play with matches.
3. We need to talk about this tomorrow.
4. That morning I had to go to the bank and so I was late for work.
5. He did not have to get up early, he had a vacation,
6, you must get off at the next stop
7. They are bound to help you in this situation.
8. Did they have to wait a long time for the train?
9. You do not need to speak Russian in English lessons.
10. We had to stay at home yesterday, because it was raining heavily,
11. They do not need to come here every day
12. Students will have to stay after school
13. Do we need to prepare reports for the next lesson? Yes.
14. When will he have to answer all the letters?
15. Adult children should take care of their parents.
16. You had to stay after work, did not you?
8-4x=4-8x
-4x+8x=4-8
4x=-4
x=-1
