Cho x 2 ,   1 2 y 2  theo thứ tự lập thành một cấp số cộng. Gọi M,m lần lượt là giá trị lớn nhất và nhỏ nhất của biểu thức 3 x y + y 2 . Tính S=M+m

A. S=1

B. S=2

C. S=3

D. S=5

Tính mô đun của số phức  z = ( 2 + i ) 2 i

A. 5

B. 10

C. 15

D. 13

Vì \(\Delta ABC\) đều \(\Rightarrow\widehat{A}=\widehat{B}=\widehat{C}=60^o\)(t/c) và AB=AC=BC (đn)

mà AD=BE=CF \(\Rightarrow\) AB-AD=BC-BE= AC- CF \(\Rightarrow\)BD=CE=AF

Có \(\Delta ADF=\Delta BED\left(c.g.c\right)\)\(\Rightarrow\) DE=EF( 2 cạnh tương ứng)

\(\Delta EBD=\Delta FCE\left(c.g.c\right)\Rightarrow\) DE=EF (2 cạnh tương ứng)

=> DE=DF=EF

=>\(\Delta DEF\) là tam giác đều

Tại cuộc thi, Ban tổ chức sử dụng 7 thẻ vàng và 7 thẻ đỏ, đánh dấu mỗi loại các số 1,2,3,4,5,6,7. Hỏi có bao nhiêu cách xếp tất cả các thẻ này thành một hàng sao cho hai thẻ cùng màu không nằm liền nhau?

A. 25401600

B. 3628800

C. 7257600

D. 50803200

I. Đặt câu hỏi cho câu trả lời theo từ đã cho:

1. Last week, I stayed at home because I was sick.

=> Why did you stay at home last week?

He talked about his school.

=> What did he talk about?

3. Mai went to the museum yesterday afternoon.

=> When did Mai went to the museum ?

4. My aunt went to bed at 12 o'clock last night

=> What time did your aunt go to bed last night?

5. I went to bed early last night because I was very tired.

=> Why did you go to bed early last night?

6. The TV program started at 8.00.

=> When did the TV program start?

7. My brother started school when he was five.

=> When did your brother start school?

8. He stayed in bed because he had a headache.

=> Why did he stay in bed?

9. Hoa left school when she was eighteen.

=> When did Hoa leave school?

10. She spent the afternoon in the library.

=> Where did she spend the afternoon?

II. Tìm và sửa lỗi sai cho đúng: ( mỗi câu đều có lỗi sai)

1. Mai is a good friend of I.

=> Mai is a good friend of me.

2. Last week, Hoa moves to a new apartment.

=> Last week, Hoa moved to a new apartment.

3. The people in Ha Noi are very friend.

=> The people in Ha Noi are very friendly.

4. Hoa thought sew was a useful hobby.

=> Hoa thought sewing was a useful hobby.

5. The children can't didn't a lot of things.

=> The children can't do a lot of things.

6. My mother bought the material and did the dress for me.

=> My mother bought the material and made the dress for me.

7. Lan is learning how to using a sewing machine.

=> Lan is learning how to use a sewing machine.

8. What did you bought in Nha Trang last week?

=> What did you buy in Nha Trang last week?

III. Đặt câu hỏi cho từ in đậm:

1. Nam is doing his homework.

=> What is Nam doing?

2. My father traveled to Tokyo by plane.

=> How did your father trave to Tokyo?

3. Hoa and Mai will come here tomorrow evening.

=> When will Hoa and Mai come here?

4. My mother was in Da Nang last week.

=> Where was your mother last week?

5. Lan left home at 6.30 yesterday morning.

=> What time did Lan leave home yesterday morning?

6. Hoa bought a cap in the souvenir shop.

=>What did Hoa buy in the souvenir shop?

7. Mr. Pike taught me English last year.

=>Who did teach you English last year?

8. My new skirt is black.

=>What color is your new skirt?

9. Mai stayed in Hue for five days.

=>How long did Mai stayed in Hue?

10. Hoa went to Ha Noi on vacation last week.

=>Where did Hoa go to on vacation last week?