Cho hình chóp S.ABCD có đáy là hình vuông cạnh a, mặt bên SAB là tam giác vuông cân tại S và nằm trong mặt phẳng vuông góc vói đáy. Gọi M là trung điểm của SC và α  là số đo của góc giữa hai đường thẳng AC, BM. Khi đó cos α bằng

Số nghiệm nguyên của bất phương trình ( 5 - 2 6 ) 2 - x x - 1 ≥ 2 6 + 5 x + 1 x + 2

A. 2.

B. 1.

C. 3.

D. Vô số nghiệm nguyên.

Sắp sếp: 

1. Flower/Is/alright?/the/Restaurant

Is the Flower Restaurant alright?

2. bit/runs/fast./He/a

He runs a bit fast.

3. is/bit/The market/far from my house./a

The market is a bit far from my house.

4. is/to cycle to school./young/Bao/too

Bao is too young to cycle to school.

5. successfully/his/Bell/invention./demonstrated 

Bell demonstrated his invention successfully.

Chọn từ phát âm sai: 

A. deaf                B. reach                   C. speak                D. dream

Chọn đáp án đúng:

1. He fell "_" and broke his leg.

A:upstair     B:upstairs    C:dowstairs    D:downstair

2. The _ of telephone made Alexander Graham Bell gamous all over the world.

A:invent      B:invented      C:intention      D:invention

3. They emigrated __ Australia in the 1960s to find work.

A: at                   B: in                  C: to                 D: for

Nhìn cũng đẹp trai!!! Ai vậy???

15^x : 5^y = 45^y

=> 15^x = 45^y * 5^y = (45 *5)^y = 225^y 

=> 15^x = 225^y 

=> 15^x  - 225^y = 0

=> x = 0, y = 0  

a ) Lan is learning to dance .

She is going to be a dancer.

b ) Hoa loves children .

Hoa is going to be a teacher.

c ) Tom and John are learning to fly

They are going to be pilots.

d ) Nam is studying law .

He is going to be a lawyer.

e ) Bob's at drama school .

Bob is going to be a actor.

f ) Peter cooks very well .

He ism going to be a chef.

g ) Loan's good at languages .

She is going to be a interpreter.

h ) Linda can run very fast .

She is going to be a runner.

i ) Thu is very good  at singing .

She is going to be a singer.

I haven't eaten any thing for breakfast.

Have you ever eaten cheese?

Has your mom ever watched this film?

We have already visited Ha Long Bay twice.

I haven't received any letters from maryam recently.

My brother hasn't never been Hanoi.

Hoang has just bought a new bike.

This is the first time I have met my pen pal.

Have you ever speaked a famous person?

Mrs. Ha has never traveled by plane.

1.    804:3+1=269(trong 1 dãy số cách đều, số trung bình luôn là số ở giữa)

2.     25x(25+5)=750(cm2)

Tổng đúng ko?