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a.S=1-2+3-4+...+99-100
=(1-2)+(3-4)+...+(99-100)
=(-1)+(-1)+...+(-1)
Vì từ 1->100 nên có 50 cặp
=> có 50 số -1
=>(-1)+(-1)+...+(-1)=-50
=>1-2+3-4+...+99-100=-50
b. n + 5 chia hết cho n - 2
n - 2 + 7 chia hết cho n - 2
Mà n - 2 chia hết cho n - 2
=> 7 chia hết cho n - 2
n - 2 thuộc Ư(7) = {-7 ; -1 ; 1 ; 7}
n - 2 = -7 => n = -5
n - 2 =-1 => N = 1
n - 2 = 1 => n = 3
n - 2 = 7 => n = 9
Vậy n thuộc {-5 ; 1 ; 3 ; 9}
It's a good idea for us to do exercises every morning.
1. Lỗi sai: isn't --> are not
2.Lỗi sai: little --> few
3. Lỗi sai: any --> some
4.Lỗi sai: any--> some; some--> any
5. Lỗi sai: few --> little
6. Lỗi sai: many --> some
7. Lỗi sai: any --> some
8. much --> many
9. Lỗi sai: some --> any
10.a lot of --> any
11.what --> where
12. a lot of --> any
13. kid --> kind
14. yoru --> your/ when --> how often
15. homework --> his homework
16. near to --> near
17. very --> any
a tent is a temporary shelter you use when you go camping.
From Nguyen Duc Hien to Luca. I had a fun weekend. My dad took me to the City Center Square. After that, my sister from China went home and gave me a lot of gift! The weather in the weekend is some cloudy and cold. But I like it so much!
From: Nguyen Duc Hien
To: Luca
1. I like Tran temple festival the most
2. Yes, it is
3. It starts on the 15th day of the 8th lunar month
4. It is held at Tran temple of Nam Dinh province
1.good
2.easier
3.longer
4.thinner
1.the best
2.easier
3.longer
4.thinner