Ta biết rẳng nếu có 2 đường thẳng đi qua nhau thì sẽ tạo ra 2 cặp góc đối đỉnh.

      Vậy nếu có n đường thẳng đi qua nhau thì có bao nhiêu cặp góc đối đỉnh?

Neu iu diem cua su thai sinh voi de trung va noan thai sinh

Neu iu diem cua su thai sinh voi de trung va noan thai sinh

-Tìm từ ghép chính phụ,từ ghép đẳng lập trong 2 bài đọc thêm "Thư gửi mẹ"và"Vì sao hoa cúc có nhiều cánh nhỏ".

trong bài "Mẹ Tôi"(ngữ văn 7,tập 1 trang 10) câu hỏi:

-Thái độ của người bố đối với En-ri-cô qua bức thư là thái độ như thế nào?Lí do gì khiến ông có thái độ ấy?

-Dựa vào đâu mà em biết được?

$\frac{1}{2+\sqrt{3}}-$$\frac{1}{2-\sqrt{3}}$

$\sqrt{{\left(2-\sqrt{3}\right)}^2}$$+ \sqrt{4-2\sqrt{3}}$

$\frac{1}{2+\sqrt{3}}$ $-\frac{1}{2-\sqrt{3}}$

Rút gọn :

$A=1+\frac{3m}{m-2}$$\sqrt{m^2-4m+4}$

B=$\left(1+\frac{1+\sqrt{a}}{\sqrt{a+1}}\right)$$\left(1+\frac{a-\sqrt{a}}{\sqrt{a}-1}\right)$

$C=$$(\frac{\sqrt{x}+1}{\sqrt{x}-1}-$$+ \sqrt{4-2\sqrt{3}}$0$+ \sqrt{4-2\sqrt{3}}$1

S= $+ \sqrt{4-2\sqrt{3}}$2$+ \sqrt{4-2\sqrt{3}}$3$+ \sqrt{4-2\sqrt{3}}$4)

a) Rút gọn S

b)Tính GT của S tại x=4-$+ \sqrt{4-2\sqrt{3}}$5

c)Tính GT của S tại x=$+ \sqrt{4-2\sqrt{3}}$6

Cho tg ABC có trực tâm H, trọng tâm G và tâm đg tròn ngoại tiếp (O) CM:

a. vecto HA + vecto HB+ vecto HC= 2. Vecto HO

b. vecto OA + vecto OB+ vecto Oc=vecto OH

Tìm lỗi sai và sửa nó

1.Jane told me that she will have to go  to London the following day

2.Tom,together with his two sisters, are going to join our trip next weekend

3. I come from a city locating in the southern part of the country 

4.Our new neightbors had been living in Arizona for 10 years after moving to their present house

Cho 15x-3y/4 =6z-20/3=6y-9z/2 

C/m x/3=y/15=z/10

chú thích  cái / là phần 

It is believed that the man was killed by terrorists.

 We didn't know about her death until he phoned us.

They were late for school because they missed the first train.

When will you return to your hometown, Nam?" She said to Nam.

They usually hold the contests at the university.

 His disabilities didn't prevent him from sailing around the world.

 They had such a fierce dog that nobody would visit them.

 I'm absolutely sure he took the money on purpose.

  The cost of livings has gone up considerable in the last few years.

 "That's a lovely new dress, Lan" said her mother.

Flooding in this region was the result of heavy rain.

They decided to build a new school in this region.

  We were late for the meeting because it rained heavily.

 It was wrong of you to allow a 4-year-old child to walk home alone.

Someone has suggested abolishing income tax.

They thought that the little girl had found out the keys accidentally.

The keys were 

Tính nhanh

Tính nhanh

She thought it was too difficult for her to finish the job by lunchtime.

She thought it was too difficult for her to finish the job by lunchtime.

She found 

( 2,5 × 12 × 0,4 ) - ( 0,125 × 5 × 8 )

Success depends on hard work.

The harder 

Scientists have tried very hard to find a cure for AIDS.