Bài 2: 

a: Xét tứ giác ABOC có

\(\widehat{ABO}+\widehat{ACO}=180^0\)

Do đó: ABOC là tứ giác nội tiếp

Bài 1: 

a: Xét ΔAMB và ΔAMC có

AM chung

AB=AC

BM=CM

Do đó: ΔABM=ΔACM

giúp, đây ko phải thi nhoa, giải chi tiết mới tick

3.Chiều rộng là:

90x3/5=54(m)

Chu vi là:
(90+54)x2=288(m)

Diện tích là:

90x54=4860(m²)

ĐS:...

Câu 3 : lười làm

Câu 4: \(\left(\dfrac{3}{5}\times\dfrac{5}{3}\right)\times\left(\dfrac{5}{6}\times\dfrac{6}{5}\right)\times\dfrac{3}{4}=1\times1\times\dfrac{3}{4}=\dfrac{3}{4}\)

Ta sẽ chứng minh bằng biến đổi tương đương như sau :

Ta có : \(\sqrt{a+b}< \sqrt{a}+\sqrt{b}\left(1\right)\Leftrightarrow\left(\sqrt{a+b}\right)^2< \left(\sqrt{a}+\sqrt{b}\right)^2\Leftrightarrow a+b< a+b+2\sqrt{ab}\)

\(\Leftrightarrow2\sqrt{ab}>0\Leftrightarrow\sqrt{ab}>0\) (luôn đúng)

Vì bất đẳng thức cuối luôn đúng nên bất đẳng thức (1) được chứng minh.

1:

Đặt AB=x; CM=y

Theo đề, ta có: 4x-4y=28 và x^2-y^2=119

=>x-y=7 và x^2-y^2=119

=>x=y+7 và y^2+14y+49-y^2=119

=>y=5

=>S=5^2=25cm²

C

C

1 a / leather / handbag / black

-> It's a black leather handbag.

2 Japanese / a / car / new / red / big / luxurious

-> It is a luxious big new red Japanese car.

3 Grey / long / bread / a

-> It's a long grey bread.

4 flowers / red / small

-> They are small red flowers.

5 beautiful / she / lips / with / full / red / is

-> She is beautiful with full red lips.

6 expensive / house beautiful / a / large

-> It's a expensive large beautiful house.

7 house / a / modern / big / brick

-> It's a big modern brick house.

8 American / a / plane / new . / blue / big / long

-> It's a new big long blue American plane.

9 table / a / round / big / white / plas

-> It's a big round white plas table.

10 fair / hair / she / long / curly / has

-> She has fair long curly hair.

Chúc em học tốt!!!

1 a / leather / handbag / black

-> It's a black leather handbag.

2 Japanese / a / car / new / red / big / luxurious

-> It is a luxious big new red Japanese car.

3 Grey / long / bread / a

-> It's a long grey bread.

4 flowers / red / small

-> They are small red flowers.

5 beautiful / she / lips / with / full / red / is

-> She is beautiful with full red lips.

6 expensive / house beautiful / a / large

-> It's a expensive large beautiful house.

7 house / a / modern / big / brick

-> It's a big modern brick house.

8 American / a / plane / new . / blue / big / long

-> It's a new big long blue American plane.

9 table / a / round / big / white / plas

-> It's a big round white plas table.

10 fair / hair / she / long / curly / has

-> She has fair long curly hair.