a) Xét Tam giác ABC và Tam giác ECM 
có:  BM = CM (M là trung điểm của BC)
       AMB = EMC ( Đối đỉnh)
       AM = EM (M là trung điểm của AE)
=> Tam giác ABC = Tam giác ECM (c. g .c) (đpcm)
b) Vì AB < AC
mà AB = EC
=> EC < AC
=>EAC < AEC (quan hệ giữa góc và cạnh đối diện )
=>MAC < MEC
Mà MAB = MEC (Tam giác ABC = Tam giác ECM)
=>MAC < MAB 

a/ Xét ΔABM và ΔECM có:

MB=MC (Mlà trung điểm của BC)

góc AMB = góc EMC ( 2 góc đối đỉnh)

MA=ME(giả thiết)

Do đó ΔABM=ΔECM(c.g.c)

b/ MAC<MAB

bạn ế thật rồi,năm nay là năm 2021 mà bạn vẫn chưa có ai trả lời

bạn ế hay sao mà 2 năm rồi chưa có ai trả lời vậy

hình 2

_ I see a man is holding a child and a woman is going to work.

_I can see that in the future, men will take care of children, cook rice, ... and women will be the backbone of the family to make money to feed everyone in the house. But today, in complete contrast, men are the breadwinner of the family, and women stay home to take care of their babies, and cook housework.

_I think this transition is not very appropriate for men, which are healthier than women, so they will do heavy work. Women are weaker than men, so they will do light work such as taking care of children , cooking rice , doing housework

hình 2

2. The problems faced by the company, which I'll look at in detail in a moment, are being resolved.

3. She was greatly influenced by her father, who/ whom she adored.

4. Parents whose children are between four and six are being asked to take part in the survey.

5. He isn't looking forward to the time when he will have to leave.

6. The Roman coins, which a local farmer came across in a field, are now on display in the National Museum.

7. He pointed to the stairs which/that led down to the cellar.

8. These drugs, which are used to treat stomach ulcers, have been withdrawn from sale.

9. The singer, who was recovering from flu, had to cancel her concert.

10. We went to the Riverside Restaurant where I once had lunch with Henry.

11. My aunt, whose first job was filling shelves in a supermarket, is now a manager of a department store.

12. John Graham‟s latest film, which is set in the north of Australia, is his first for more than five years.

13. The newspaper is owned by the Mears group, whose chairperson is Sir James Hex.

14. The Master's course, which I took in 1990, is no longer taught.

15. The minister talked about the plans for tax reform (that/which) he will reveal next month.

2. The problems faced by the company, which I'll look at in detail in a moment, are being resolved.

3. She was greatly influenced by her father, who/ whom she adored.

4. Parents whose children are between four and six are being asked to take part in the survey.

5. He isn't looking forward to the time when he will have to leave.

6. The Roman coins, which a local farmer came across in a field, are now on display in the National Museum.

7. He pointed to the stairs which/that led down to the cellar.

8. These drugs, which are used to treat stomach ulcers, have been withdrawn from sale.

9. The singer, who was recovering from flu, had to cancel her concert.

10. We went to the Riverside Restaurant where I once had lunch with Henry.

11. My aunt, whose first job was filling shelves in a supermarket, is now a manager of a department store.

12. John Graham‟s latest film, which is set in the north of Australia, is his first for more than five years.

13. The newspaper is owned by the Mears group, whose chairperson is Sir James Hex.

14. The Master's course, which I took in 1990, is no longer taught.

15. The minister talked about the plans for tax reform that he will reveal next month.

1. Ann is very friendly. She lives next door.

Ann who lives next door is very friendly

2. The man is a famous actor. You met him at the party last night.

The man whom you met at the party last night is a famous actor

3. There are some words. They are very difficult to translate.

There are some words which are very difficult to translate

4. The sun provides us with heat and light. It is one of millions of stars in the universe.

The sun, which is one of millions of stars in the universe, provides us with heat and light

5. Students will be punished. Their homework is late.

 Students who homework is late will be punished

6. I was looking for a book this morning. I've found it now.

I've found the book I was looking for this morning

7. Is that the car? You want to buy it.

  Is that the car which you want to buy ?

8. Sandra works in advertising. You were talking to her.

Sandra, who you were talking to, works in advertising.

9. Lake Prespa is a lonely beautiful lake. It‟s on the north Greek border.

Lake Prespa, which is a lonely beautiful lake, is on the north Greek border

10. The little girl ate sweets the whole way. She sat next to me on the coach.

The little girl who sat next to me on the coach ate candy the whole way

1. Ann, who lives next door, is very friendly.

2. The man who/that you met at the party last night is a famous actor.

3. There are some words that/which are very difficult to translate.

4. The sun, which is one of millions of stars in the universe, provides us with heat and light.

5. Students whose homework is late will be punished.

6. I've found the book that/which I was looking for in the morning.

7. Is that the car that/which you want to buy?

8. Sandra, who you were talking to, works in advertising.

9. Lake Prespa, which is on the north Greek border, is a lonely beautiful lake.

10. The little girl who/that sat next to me on the coach ate sweets the whole way.

A B C D 4 9 E I

a, Xét tam giác ABD và tam giác BDC ta có : 

^BAD = ^CBD ( gt )

^ABD = ^BDC ( so le trong )

Vậy tam giác ABD ~ tam giác BDC ( g.g )

\(\Rightarrow\frac{AB}{BD}=\frac{BD}{DC}\)( tỉ số đồng dạng ) \(\Rightarrow BD^2=AB.DC=4.9=36\)

\(\Rightarrow BD=\sqrt{36}=6\)cm 

b, Gọi giao điểm AC và BD là I

Xét tam giác BIE và tam giác AID có : BE // AD 

Theo hệ quả Ta lét ta có : \(\frac{BI}{ID}=\frac{IE}{IA}=\frac{BE}{AD}\)

Xét tam giác AIB và tam giác DIC có AB // CD ( ABCD là hình thang )

\(\frac{AI}{IC}=\frac{IB}{ID}=\frac{AB}{DC}\)

mà \(\frac{BE}{AC}=\frac{AB}{DC}=\frac{IB}{ID}\Rightarrow BE.DC=AB.AC\)

M N P 3 4 H D K

a, Xét tam giác NMP vuông tại M, có đường cao MH 

Áp dụng định lí Py ta go ta có : 

\(NP^2=MN^2+MP^2=9+16=25\Rightarrow NP=5\)cm 

Vì ND là đường phân giác nên : \(\frac{MN}{NP}=\frac{MD}{DP}\)mà \(DP=MP-MD=4-MD\)

hay \(\frac{3}{5}=\frac{MD}{4-MD}\Rightarrow12-3MD=5MD\)

\(\Leftrightarrow8MD=12\Leftrightarrow MD=\frac{12}{8}=\frac{3}{2}\)cm 

b, Xét tam giác MHN và tam giác MNP ta có :

^NHM = ^NMP = 90⁰

^N _ chung 

Vậy tam giác MHN ~ tam giác MNP ( g.g )

c, Xét tam giác NDM và tam giác NKH ta cs : 

^MNP = ^NHK = 90⁰

\(\frac{MN}{NH}=\frac{MK}{KH}\)( NK là đường phân giác )

Vậy tam giác NDM ~ tam giác NKH ( c.g.c )

\(\Rightarrow\frac{ND}{NK}=\frac{NM}{NH}\)( tỉ số đồng dạng ) \(\Rightarrow ND.NH=NM.NK\)