Cho (R1 nt R2)// R3.
U= 220V; R1= \(30\Omega\) ; R2= \(40\Omega\) ; R3= \(70\Omega\)
R tương đương = ?
I, I1, I2, I3 = ? A

Cho tứ giác ABCD có góc A= Góc C= 90 độ
a) Chứng minh bốn đỉnh của tứ giác cùng thuộc 1 đường tròn
b) Chứng minh AC nhỏ hơn hoặc bằng BD
c) Nếu AC=BD thì tứ giác ABCD là hình gì ?

Cho 5.5g hỗn hợp gồm 2 loại là MgCO3, MgSO4 tác dụng với 200ml dd H2SO4. Sau phản ứng thu được 3.36l khí (đktc).
a. Tính C% khối lượng của hỗn hợp ban đầu.
b.Tính CM dd H2SO4.

What should you do to keep your school clean ?

1.Vitamin intake and intelligence are not connected.
- There is
2.The train couldn't run because of the storm.
- The storm prevented
3.My mother doesn't have anyone make clothes for her.
- My mother makes
4.Although he had a good salary, he was unhappy in his job.
- In spite of

1.The film star wore dark glasses so that no one would reconise him.
- The film star avoided
2.He forgot about the bag until he got home.
- Not until
3.I tried as hard as i could, but I just couldn't get the money.
- No matter
4.There are a number of people waiting to see you now.
- A number of people

1. There's no point in asking Ms.Hoa to help.
- It isn't...
2.Khanh's behavior at the party annoyed us.
- We were...

Identify the error in the following sentences.
1. The number of the studens who have got bad marks since Chrismast are appalling.
A B C D

2.I tried to do everything to contact John two weeks ago but so far I don't receive his reply.
A B C D

3. It's high time people pay much attention to education.
A B C D

4. The letter was sent by special delivery must be important.
A B C D

5. The harder he tried, the worst he danced before the large audience.
A B C D