\(A=\frac{1}{2}+^{^{^{ }}}\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}\)

\(2A=1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}\)

\(2A-A=1-\frac{1}{2^4}\)

\(A=1-\frac{1}{16}=\frac{15}{16}\)

Bạn tự vẽ hình nhé ! 
Ta có tia Oy nằm giữa 2 tia Ox và Oz ( \(\widehat{xOy}< \widehat{xOz}\left(50^0< 130^0\right)\) ) 
=> \(\widehat{zOy}=\widehat{xOz}-\widehat{xOy}\)
=> \(\widehat{zOy}=130^0-50^0=80^0\)
Ta lại có : Ot là tia đối của tia Oy 
=> \(\widehat{tOy}=180^0\)
=>\(\widehat{zOt}+\widehat{zOy}=\widehat{tOy}\)
=> \(\widehat{zOt}=180^0-80^0=100^0\)

Ta có : 44²⁰ = ( 44² ) ¹⁰ = 1936¹⁰
Vì 1936 chia 15 dư 1 , mũ bao nhiêu cũng vẫn vậy 
=> 1946¹⁰ chia 15 dư 1 
<=> 44²⁰ chia 15 dư 1

 

Có tớ 

1. There are three collections a day from the post box on the corner.                    (collect)

2. We have to leave the party hurriedly or we'll miss the bus.                            (hurry)

3. The holiday was so disappointing that they decided to asked for money back.                 (disappoint)

4. I can see the similarity between you and your mother.                               (similar)

5. Everyone felt tired and hungry so they sat down under the tree and had a snack.                   (hunger)

     Minh is my new classmate. He is now staying (1) with  his brother in Ha Noi, but he's (2) lived in Bac Giang Town and his parents still (3)living . there.

     Minh's brother's house is smaller (4) than  his house in Bac Giang, and it is on Xuan Thuy Street. Our (5) school  is in the center of Ha Noi, so (6) it is about 8 kilometers from his new house (7) to school. Every day Minh goes to school (8) by bike. Minh is unhappy because he doesn't (9) have  many friends in Ha Noi. He also (10)misses his parents and his friends in Bac Giang.

1.goes/ bus/ Hoang/ day/ work/ Mr./ every/ to/ by.
Mr.Hoang goes to work by bus every day  

2.new/ from/ one/ is/ house/ his/ how / different/ Minh's/ old.
Minh's new house is how different from his old one .

3.because/ parents/ is/she/ Nguyet/ misses/ unhappy/ her.
Nguyet is unhappy because she misses her parents

4.friends/ town/ lot/ does/ her/ Nhung/ of/ in/ a /have?
Does Nhung have a lot of friends in her town ?

5.lunch/ o'clock/ going/ it's/ and/ the/ twelve/ we're/ to/room.
It's twelve o'clock and we're going to the lunch room 

1-141/893= 16/19   ,   1-159/901=14/17

Vì 16/19 > 14/17 nên 159/893 > 141/893

Theo đề ra ta có dạng tổng sau :
1 + 3 + 5 + .... + n = 100
= ( 1 + n ) . [( n - 1 ) : 2 + 1 ] : 2 = 100 
=> ( 1 + n ) ( n + 1 ) = 400 
=> n + 1 = 20 
=> n = 19 
Vậy : dãy số lẻ liên tiếp bằng 100  là : 1 + 3 + 5 + .... + 19   
 

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