5 x 5 = 25

3 x 5 = 15

1. we are going to stay with our grandparents next sumer vacation
2. the Nile River is the longest river in the world 
3. let's go to a beach and have a good time
4. his sister has small white teeth and thin lips
5. this sign say "no parking" so we mustn't park here
6. john always feels happy when he comes home
7. my sister rides home and has lunch at a quarter to twelve
8. a notebook is usually cheaper than a dictionary
9. there isn't much water in the bottle
10. i am still hungry and i need some more rice

Câu a :  

\(\dfrac{5}{12}+\dfrac{3}{4}+\dfrac{1}{3}\\ =\dfrac{5}{12}+\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{3}{2}\)

câu b : 

\(\dfrac{1}{4}+\dfrac{3}{7}+\dfrac{11}{14}\\ =\dfrac{7}{28}+\dfrac{12}{28}+\dfrac{22}{28}=\dfrac{41}{28}\)

câu c : 

\(\dfrac{1}{4}+\dfrac{3}{12}+\dfrac{12}{36}\\ =\dfrac{3}{12}+\dfrac{3}{12}+\dfrac{4}{12}\\ =\dfrac{10}{12}=\dfrac{5}{6}\)

viết lại câu : 
1.  tim doesn’t play football as well as mark
2. when did you play basketball
3/ i am interested in playing basketball than my brother
sắp xếp từ : 
1. did you watch the men's basketball final on tv last night 
2. last week, we studied how to surf. it was very interesting
3. where were the children on yesterday morning ? they were at the swimming pool
4. his father taught him how to play football when he was a very young age 

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câu 2 : 

a) có phải là chứng minh AM ⊥ BC không

xét ΔAMB và ΔAMC, ta có : 

AB = AC (2 cạnh bên của ΔABC cân tại A)

MB = MC (AM là đường trung tuyến của cạnh BC)

AM là cạnh chung

=> ΔAMB = ΔAMC (c.c.c)

=> \(\widehat{AMB}=\widehat{AMC}\) (2 cạnh tương ứng)

mà \(\widehat{AMB}+\widehat{AMC}=180^O\) (kề bù)

\(\Rightarrow\widehat{AMB}=\widehat{AMC}=\dfrac{180^O}{2}=90^O\)

=> AM ⊥ BC

1. he is an american
2. - i visit my friends on fridays
- when's your birthday ?
- it's on february 4th
3. minh quan and diep chi are vietnamese
4. tên của tháng mười là gì 

xét ΔECB và ΔDBC, ta có : 

EC = BD (gt)

\(\widehat{B}=\widehat{C}\) (2 góc đáy của ΔABC cân tại A)

BC là cạnh chung

=> ΔECB = ΔDBC (c.g.c)

=> \(\widehat{GBC}=\widehat{GCB}\) (2 góc tương ứng)

vì ΔGBC có \(\widehat{GBC}=\widehat{GCB}\) nên ⇒ ΔGBC là một tam giác cân (cân tại G)