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a: Xét tứ giác AEHF có
\(\widehat{AEH}=\widehat{AFH}=\widehat{FAE}=90^0\)
Do đó: AEHF là hình chữ nhật
![](https://rs.olm.vn/images/avt/0.png?1311)
TL:
Sai nhé bạn
Bạn k cho mik cái đi nhé
@@@@@@@@@@@@@@@@@
HT
![](https://rs.olm.vn/images/avt/0.png?1311)
ờ...tớ ko nhầm thì thừa are
nếu bỏ are thì she's making a papper boat
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a) \(\dfrac{3}{4}+\dfrac{9}{5}\div\dfrac{3}{2}-1=\dfrac{3}{4}+\dfrac{18}{15}-1=\dfrac{39}{20}-1=\dfrac{19}{20}\)
b) \(\dfrac{6}{7}\cdot\dfrac{8}{13}+\dfrac{6}{13}\cdot\dfrac{9}{7}-\dfrac{4}{13}\cdot\dfrac{6}{7}=\dfrac{48}{91}+\dfrac{54}{91}-\dfrac{24}{91}=\dfrac{48+51-24}{91}=\dfrac{78}{91}=\dfrac{6}{7}\)
c) \(\dfrac{-3}{7}+\left(\dfrac{3}{-7}-\dfrac{3}{-5}\right)\)\(=\dfrac{-3}{7}+\left(\dfrac{-3}{7}-\dfrac{-3}{5}\right)=\dfrac{-3}{7}+\dfrac{6}{35}=-\dfrac{9}{35}\)
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1 do you do
2 had done - went
3 went - had read
4 will attend
5 hadn't worn
6 to be
7 weren't sleeping - were playing
8 to be
9 had lived - moved
10 locking
11 had work - retired
12 told - had learned
13 won't call
14 had met
do you do
had done-went
went- had read
will attend
hadn't worn
to be
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1 How long do you live in HN
2 How often did you go to the movies
3 What did Mrs Robinson buy
4 When was your father in Nghe An
5 How do they go to school
6 Why didn't she go to class
7 Who left home at 7o'clock yesterday
8 What subject does he study in the high school
9 What is your favorite hobby
10 How far is it
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3. are there any eggs?-No, there aren't some
4.is there any salt?- yes, there is any
5.are there any carrots?-yes, there are some
6.are there any apples?-no there aren't some
7.is there any suger?-yes, there is any
8.are there any cakes?-no there aren't some
9.is there any butter?-no. there isn't any
10. is there any mineral water?- yes. there is any
a)1/1.2+1/2.3+1/3.4+....+1/1999.2000
=1-1/2+1/2-1/3+1/3-1/4+....+1/1999-1/2000
=1-1/2000
= Bn tự tính
b)=1/3.(1/1.4+1/4.7+1/7.10+...+1/100+103)
=1/3.(1-1/4+1/4-1/7+1/7-1/10+...+1/100-1/103)
=1/3.(1-1/103)
= tự làm
c)8/9-1/72-1/56-1/42-...-1/6-1/2
=8/9-(1/2+1/6+...+1/42+1/56+1/72)
=làm tương tự phần trên. Gợi ý :72=8.9 . Nói đến thế r mà ko bt làm thì chịu. yên tâm, đảm bảo đ, t học đội tuyển mà
a) \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{1999.2000}\)
\(=\frac{2-1}{1.2}+\frac{3-2}{2.3}+\frac{4-3}{3.4}+...+\frac{2000-1999}{1999.2000}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{1999}-\frac{1}{2000}\)
\(=1-\frac{1}{2000}=\frac{1999}{2000}\)
b) \(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{100.103}\)
\(=\frac{1}{3}\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{100.103}\right)\)
\(=\frac{1}{3}\left(\frac{4-1}{1.4}+\frac{7-4}{4.7}+\frac{10-7}{7.10}+...+\frac{103-100}{100.103}\right)\)
\(=\frac{1}{3}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{100}-\frac{1}{103}\right)\)
\(=\frac{1}{3}\left(1-\frac{1}{103}\right)\)
\(=\frac{34}{103}\)
c) \(\frac{8}{9}-\frac{1}{72}-\frac{1}{56}-...-\frac{1}{6}-\frac{1}{2}\)
\(=\frac{8}{9}-\left(\frac{1}{8.9}+\frac{1}{7.8}+...+\frac{1}{2.3}+\frac{1}{1.2}\right)\)
\(=\frac{8}{9}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\right)\)
\(=\frac{8}{9}-\left(1-\frac{1}{9}\right)=0\)