I D C A B H M K

Bài làm:

Từ A kẻ đường vuông góc với DM cắt DM tại K

Mà AB // KH và AK // BH ( vì cùng vuông góc với DM ) ; góc AKH = 90 độ

=> ABHK là hình chữ nhật

=> AB = HK (1)

Δ ADK = Δ BCH ( c.h-g.n)

=> DK = HC

Mà DH = HM <=> DK + KH = HC + CM

=> KH = CM (2)

Từ (1) và (2) => AB = CM, mà AB // CM

=> Tứ giác ABMC là hình bình hành

=> BM = AC

Last summer, I went to Nha Trang beach with my family , it was such a memorable summer holiday. We went there by car , and when we nearly got there, from the far distance , I could see how wide and beautiful the beach was. The weather was so nice that made me want to run directly to the beach, enjoy the fresh air and clean water. There were a lot of people swimming , sunbathing, playing volleyball on the shore , and some children even built sand castles and flew kites .We stayed at Edele hotel whose service I found very satisfied and I had the chance to eat the sea food there , they were very delicious . I went to Vinpearl Land , Long Sơn pagoda,too .They were very wonderful. I felt very fun and happy because I also met many foreigners ,they were tourists and I had talked to them a lot . We stayed in Nha Trang for a week and the last day , I went to some gift shop near the beach to buy souvenir for my grandparents and my friends . When I came back home , I felt very happy but a little regretted because I wanted to stay there longer. I told my dad I d Nha Trang and I hoped we can go to Nha Trang again one summer .

LÀM

Last summer , my parents took me to Phu Quoc for a week . Phu Quoc - dubbed as Ngoc Island . Here the many species of birds , with unique dishes . And the people there as well . They are interesting . It is also known as the paradise of sunshine and wind . The week passed quickly , and it was time for me to go home . But I can not forget the funny and strange things that are only available in Phu Quoc . Heaven of sunshine and wind 

HỌC TỐT !!!

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Bg

|2x - 4| = 25 - 7y² 

Ta có |2x - 4| > 0

=> 7y² < 25

=> y² < \(\frac{25}{7}\)

=> y² < 3

=> y = -1 hay y = 0 hay y = 1

Nhận thấy |2x - 4| chẵn

=> 25 - 7y² chẵn

=> y lẻ

=> y = -1 hoặc y = 1

=> y² = 1

Thay vào:

|2x - 4| = 25 - 7.1

|2x - 4| = 25 - 7

|2x - 4| = 18

=> 2x - 4 = 18 hay -18

     2x       = 18 + 4 hay -18 + 4

     2x       = 22 hay -14

       x       = 22 : 2 hay -14 : 2

       x       = 11 hay -7

Vậy với y = -1 hay y = 1 thì x = 11 hay x = -7 

1+5+9+15+20+32+18+53+21+6=x+216

180=x+216

x+216=180

x=180-216

x=-36

vậy x=-36

180 = x + 216

x = 216 - 180

x = 36

1. \(A=\left(a+b\right)^2+\left(a+b\right)^2\)

\(\Leftrightarrow A=2\left(a^2+2ab+b^2\right)\)

\(\Leftrightarrow A=2a^2+4ab+2b^2\)

2. \(B=\left(a+b\right)^2-\left(a-b\right)^2\)

\(\Leftrightarrow B=\left(a+b+a-b\right)\left(a+b-a+b\right)\)

\(\Leftrightarrow B=2a.2b=4ab\)

1) \(A=\left(a+b\right)^2+\left(a+b\right)^2\)

\(A=a^2+2ab+b^2+a^2+2ab+b^2\)

\(A=2a^2+4ab+2b^2\)

2) \(B=\left(a+b\right)^2-\left(a-b\right)^2\)

\(B=a^2+2ab+b^2-a^2+2ab-b^2\)

\(B=4ab\)

a. 2x^2 ( 5x^3 - 4x^2 - 7xy + 1 )

= 10x^5 - 8x^4 - 14x^3y + 1

b. ( x - 5 ) ( x + 3 )

= x^2 + 3x - 5x - 15

= x^2 - 2x - 15

c. ( x - 1 ) ( x + 2 )

= x^2 + 2x - x - 2

= x^2 - x - 2

d. ( 2x + y ) ( 2x - y )

= 4x^2 - 2xy + 2xy - y^2

= 4x^2 - y^2

a) \(2x^2\left(5x^3-4x^2.g-7xy+1\right)\)

\(=10x^5-8x^4.g-14x^3y+2x^2\)

b) \(\left(x-5\right)\left(x+3\right)\)

\(=x^2+3x-5x-15\)

\(=x^2-2x-15\)

c) \(\left(x-1\right)\left(x+2\right)\)

\(=x^2+2x-x-2\)

\(=x^2+x-2\)

d) \(\left(2x+y\right)\left(2x-y\right)\)

\(=4x^2-y^2\)

a)

câu có sáu tiếng, câu có tám tiếng

b)

câu sáu tiếng đứng trước, câu tám tiếng đứng sau

6 là lục, 8 là bát

=> lục bát

      anh đi anh nhớ quê nhà

                                                                  nhớ canh rau muống,nhớ cà dầm tương.

                                                                              nhớ ai dãi nắng dầm sương

                                                                  nhớ ai tát nước bên đường hôm nao.

2.trả lời câu hỏi 

a)cặp câu thơ lục bát mỗi dòng có mấy tiếng ?

Cặp thơ lục bát mỗi dòng có 6 tiếng , mỗi dòn có 8 tiếng.

vì sao lại gọi là lục bát?

Vì : thể thơ có sáu chữ : Lục

Và tám chữ tiếp diễn : Bát .

14×25×6×7

=350×6×7

=2100×7

=14700

125×98×2×8×25

=12250×2×8×25

=24500×8×25

=196000×25

=4900000

A.15960

B.5140000

hỏi cho vui

(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10+20

20+20+20+20+20+20+20+20+20+10+20

210