Xem hình 74a, các mũi tên hướng dẫn cách ghép các cạnh với nhau để có được một hình lập phương.

Hãy điền thêm vào hình 74b các mũi tên như vậy.

(x²+2x)²+9x²+18x+20

=(x²+2x)²+9(x²+2x)+20

Đặt t=x²+2x ta được:

t²+9t+20=t²+4t+5t+20

=t.(t+4)+5.(t+4)

=(t+4)(t+5)

thay t=x²+2x ta được:

(x²+2x+4)(x²+2x+5)

Vậy (x²+2x)²+9x²+18x+20=(x²+2x+4)(x²+2x+5)

1/

2/ The cassette made in Japan is good.

3/ A letter was recived by Mary in this morning.

4/ The old bycyle will be repaired by my father next year.

5/ Studying French is very interesting.

7/ I couldn't read the book written in English.

8/ The drink cans be brought back for recycling.

9/ The girl reading a book is Nga.

11/ I haven't met Mr John since 2010.

12/ The man wrote this poem is my uncle.

( Còn câu 6,1,10 tớ sẽ cố gắng để trả lời sau)

1. The bridge is small enough to join two mountainous trible.

2. Do you know the man wearing black sunglasses.

3. The woman cooking in the kitchen is my aunt.

4. The time of the meeting has been changed.( bỏ by them)

5. Large areas of forest are destroyed every day.( bỏ luôn tân ngữ By people)

6. The plants should be watered every day.

1. As soon as you're heard any news can you let me know?( câu này mình cũng không chắc lắm)

2. I think it will rain. The sky is so cloudy.

3. We haven't gotten in touch with him for years.

4. Your eyes are red have you cried? ( câu này mình không chắc lắm!)

5. They need to paint these pieces of furniture.

Phát biểu định lí về tổng ba góc của một tam giác, tính chất góc ngoài của tam giác.