Nguyễn Thị Minh Nguyệt

Ta có: \(\overrightarrow{u_d}=\left(-1;2\right)=>\overrightarrow{n_d}\left(2;1\right)\)

(d): 2x + y -5 =0

Phương trình AD qua K và // BC: 5x + 2y -18 = 0

=> Tọa độ điểm A là nghiệm của hệ: \(\left\{{}\begin{matrix}2x+y-5=0\\5x+2y-18=0\end{matrix}\right.\)

⇔ \(\left\{{}\begin{matrix}x=8\\y=-11\end{matrix}\right.\) => A(8; -11)

=> OA = \(\sqrt{\left(0-8\right)^2+\left(0+11\right)^2}\) = \(\sqrt{185}\)

1. The story which was told by my friend is interesting

2. The baby who is crying in the room is very small

3. The tree which was cut yesterday is big

\(\left\{{}\begin{matrix}x^2+3x-xy=0\\xy+x+3=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x^2+3x+x+3=0\\xy=-x-3\end{matrix}\right.\)

⇔\(\left\{{}\begin{matrix}\left[{}\begin{matrix}x=-1\\x=-3\end{matrix}\right.\\xy=-x-3\end{matrix}\right.\) ⇔ \(\left[{}\begin{matrix}\left\{{}\begin{matrix}x=-1\\y=2\end{matrix}\right.\\\left[{}\begin{matrix}x=-3\\y=0\end{matrix}\right.\end{matrix}\right.\)

IV,

1. No, it wasn't

2. Two French brothers, Louis and Auguste Lumie

3. In the 1927

4. Because of the arrival of television in 1950s

V,

1. Why were the girls very happy?

2. Who are working in the field now ?

3. How long has Mary learned English ?

4. It was not until 2.30 that someone could leave the stadium

5. It was not until the age of 24 that Mary stopped learning Germen

6. It was not until their parents came home that they cleaned their house

Phân tích các lực tác dụng vào vật gồm có: N, P , F (nhớ vẽ trong hình nha)

Chọn hệ trục Oxy (vẽ vào hình luôn)

Áp dụng hệ quả định luật II Niu - tơn:

\(\overrightarrow{F}+\overrightarrow{N}+\overrightarrow{P}=m\overrightarrow{a}\) (*)

Chiếu phương trình (*) lên Ox: F = ma => a = 2,5 (m/s²)

Ta có: v² - v₀² = 2aS => v = \(5\sqrt{2}\) (m/s)

Chọn mốc thế năng trọng trường tại mặt đất

Gọi vị trí mà sợi dây hợp với phương thẳng đứng góc 45^o là A

Gọi vị trí mà sợi dây hợp với phương thẳng đứng góc 30^o là M

a. Áp dụng định luật bảo toàn cơ năng cho vật tại A và M: W_A = W_M

=> \(v_M=\sqrt{2gl\left(cos30-cos45\right)}\) ≃ 1,8 (m/s)

b. Gọi vị trí cân bằng là B

Áp dụng định luật bảo toàn cơ năng cho vật tại A và B: W_A = W_B

mgl (1 - cos45) = \(\frac{mv^2_B}{2}\) ⇔ v_B ≃ 2,42 (m/s)

c. T = mg (3cos0 - 2cos45) = \(\frac{3-\sqrt{2}}{2}\) (N)

Chọn mốc thế năng trọng trường tại mặt đất

Gọi vị trí của vật lúc đầu là O, vị trí lúc W_t = Wđ là M

Do chuyển động không có ma sát nên áp dụng định luật bảo toàn cơ năng cho vật tại O và M: W_O = W_M = 2W_t

=> mgh_O = 2mgh_M => h_M = 5 m

1. It was not until Mark helped me that I finished my project

2. It was not until the electricity was cut off that they paid the bill

3. It was not until midnight that I slept

4. It was not until I had all the information that I could comment further

5. It was not until the war ended that he returned to his native village

1. It was not until I went to university that I liked chocolate

2. It was not until 2.30 that someone could leave the stadium

3. It was not until her birthday that she was allowed to open her presents

4. It was not until last summer that we had some holidays

5. It was not until the age of 24 that she stopped learning German

1. It was not until that morning that she recovered her confidence

2. It was not until half past time that he arrived at the office

3. It was not until 2004 that Mary worked for the UN

4. It was not until I was 15 that I knew how to ride a bicycle

5. It was not until last Saturday that John finished reading my book

1. As fluently as

2. As quickly as

3. As clearly as

4. As carefully as

5. As accurately as

1. The worst

2. The best

3. The most fluently

4. The most beautifully

5. The best

1. More happily

2. More clearly

3. More highly

4. More carefully

5. Better

1. Earlier/ the earliest

2. More quickly/ the most quickly

3. More carefully/ the most carefully

4. More accurately/ the most accurately

5. More fluently/ the most fluently

6. More dangerously/ the most dangerously

7. More clearly/ the most clearly

8. Nearer/ the nearest

9. More often/ the most often

(Hình em tự vẽ nha)

1, Vì ΔCEK vuông tại K nên \(\widehat{CEK}+\widehat{ECK}=90^o\left(1a\right)\)

Mặt khác: \(\widehat{ACH}+\widehat{ACE}+\widehat{ECK}=180^o=>\widehat{ACH}+\widehat{ECK}=90^o\left(1b\right)\)

Từ (1a), (1b) suy ra: \(\widehat{CEK}=\widehat{ACH}\)

Xét hai tam giác vuông ACH và CEK bằng nhau (ch-gn)

=> AH = CK (Đpcm)

2. Theo chứng minh câu 1, ΔACH = ΔCEK => CH = EK (2a)

Vì tam giác DIB vuông tại I nên \(\widehat{IDB}+\widehat{DBI}=90^o\)

Mặt khác: \(\widehat{DBI}+\widehat{ABH}=90^o\)

=> \(\widehat{IDB}=\widehat{ABH}\)

Xét hai tam giác vuông IDB và HBA bằng nhau (ch-gn)

=> DI = BH (2b)

Do H nằm giữa B và C nên: CH + BH = BC (2c)

Thay (2a), (2b) vào (2c) suy ra: BC = DI + EK (Đpcm)

3. Xét tam giác DTE có \(\widehat{EDT}=\widehat{DET}=45^o\)

=> Δ DTE vuông cân tại T

Để A, H, T thẳng hàng ⇔ HT // EK

=> \(\widehat{HTC}=\widehat{CEK}=\widehat{ACH}\)

=> AH = TH => ΔATC có CH vừa là đường cao, vừa là đường phân giác => ΔATC cân tại C => ΔABC = ΔTBC (c-g-c)

=> \(\widehat{BAC}=\widehat{BTC}=90^o\) => ΔABC vuông tại A

Dinner was being prepared with my friends when I came

a. \(\sqrt{\left(x-1\right)\left(4-1\right)}>x-2\) ⇔ \(\sqrt{-x^2+5x-4}>x-2\)

ĐK: 1 ≤ x ≤ 4 (1)

BPT ⇔ \(\left[{}\begin{matrix}x-2< 0\\\left\{{}\begin{matrix}x-2>0\\-x^2+5x-4>x^2-4x+4\end{matrix}\right.\end{matrix}\right.\)

⇔ \(\left[{}\begin{matrix}x< 2\\\left\{{}\begin{matrix}x>2\\\frac{9-\sqrt{17}}{4}< x< \frac{9+\sqrt{17}}{4}\end{matrix}\right.\end{matrix}\right.\) ⇔\(\left[{}\begin{matrix}x< 2\\2< x< \frac{9+\sqrt{17}}{4}\end{matrix}\right.\) (2)

Từ (1), (2) suy ra: \(\left[{}\begin{matrix}1\le x< 2\\2< x< \frac{9+\sqrt{17}}{4}\end{matrix}\right.\) ⇔ x ∈ (1; \(\frac{9+\sqrt{17}}{4}\))\(|\left\{2\right\}\)

b. ĐK: -3 ≤ x ≤ 4 (1)

BPT ⇔ \(\left\{{}\begin{matrix}x-11\ge0\\12+x-x^2\le\left(x-11\right)^2\end{matrix}\right.\) ⇔ \(\left\{{}\begin{matrix}x\ge11\\\forall x\end{matrix}\right.\) ⇔ x ≥ 11 (2)

Từ (1), (2) suy ra: BPT vô nghiệm

c. ĐK: x ≤ -2, x ≥ 2 (1)

BPT ⇔ (x -3)\(\sqrt{x^2-4}\) ≤ (x - 3)(x + 3)

- Xét x = 3 là nghiệm của BPT (2)

- Xét x≠ 3, BPT ⇔ \(\sqrt{x^2-4}\) ≤ x + 3

⇔ \(\left\{{}\begin{matrix}x+3\ge0\\x^2-4\le\left(x+3\right)^2\end{matrix}\right.\) ⇔ \(\left\{{}\begin{matrix}x\ge-3\\x\ge\frac{-5}{2}\end{matrix}\right.\) ⇔ x ≥ \(\frac{-5}{2}\) (3)

Từ (1), (2), (3) suy ra BPT có nghiệm: x ∈ \([\frac{-5}{2};4]\)

Gọi hình bình hành ABCD có A(4; -1)

Nhận thấy: A∉ (d1) x - 3y = 0; A∉ (d2); 2x + 5y + 6 =0

=> d1; d2 là BC và DC

Giả sử: BC: x -3y =0 ; CD: 2x + 5y +6 =0

=> Tọa độ đỉnh C là nghiệm của hệ: \(\left\{{}\begin{matrix}x-3y=0\\2x+5y+6=0\end{matrix}\right.\)

=> C(\(\frac{-18}{11};\frac{-6}{11})\)

Phương trình AD: x + 3y -1 = 0

=> Tọa độ đỉnh D là nghiệm của hệ: \(\left\{{}\begin{matrix}x+3y-1=0\\2x+5y+6=0\end{matrix}\right.\)

=> D(-23 ; 8)

Phương trình AB: 2x + 5y - 3 = 0

=> Tọa độ đỉnh B là nghiệm của hệ: \(\left\{{}\begin{matrix}2x+5y-3=0\\x-3y=0\end{matrix}\right.\)

=> B(\(\frac{9}{11};\frac{3}{11})\)

1. B 2. D 3. B 4. B 5. C 6. A

7. B 8. B 9. A 10. C 11. D 12. D

13. C 14. B 15. A

1. Their work should be finished soon.

2. I wanted to buy the car because it was beautiful.

3. The table which I bought is expensive

4. I would phone Tom if I had his number.

5. The girl whom you are talking to is very intelligent.

6. She goes to school although she is not well

7. If we had an umbrella, we wouldn't be wet

8. If the air were pure, we would be healthy.

9. He didn't come even though we tried to invite him to party.

10. The teacher suggests taking part in social activities.

11. Although the room is very small, it is quite comfortable

12. Shall we go to the movie tonight?

13. She wishes she could swim well

14. Rice is grown in tropical countries

15. Amstrong who first walked on the moon lives in the USA

\(\overrightarrow{n_{d1}}=\left(1;2\right)\) ; \(\overrightarrow{n_{d2}}=\left(3;m\right)\)

Ta có: cos(d₁;d₂) = \(\left|cos(\overrightarrow{n_{d1};}\overrightarrow{n_{d2}})\right|\) = \(\frac{\sqrt{2}}{2}\)

=> \(\frac{3+2m}{\sqrt{\left(3+m^2\right)5}}\) = \(\frac{\sqrt{2}}{2}\) ⇔ 2(3 + 2m) = \(\sqrt{10\left(3+m^2\right)}\)

=> ĐK: 3 + 2m > 0 ⇔ m > \(\frac{-3}{2}\)

Phương trình BC: 3x + 4y - 4 =0

=> d(A; BC) = \(\frac{\left|3.1+4.4-4\right|}{\sqrt{3^2+4^2}}\) = 3

=> Đáp án C

ĐK: 2x -1 ≥ 0 ⇔ x ≥ \(\frac{1}{2}\)

\(\left(x-1\right)\sqrt{2x-1}=3\left(x^2-5x+4\right)\)

⇔ (x -1)\(\sqrt{2x-1}\) = 3(x - 4)(x - 1)

- Xét x = 1 ta thấy là nghiệm của phương trình (1)

- Xét x≠ 1: \(\sqrt{2x-1}=3\left(x-4\right)\) (x ≥ 4)

⇔ 2x -1 = 9x² -72x + 144

⇔\(\left[{}\begin{matrix}x=5\left(TM\right)\left(2\right)\\x=\frac{29}{9}\left(KTM\right)\end{matrix}\right.\)

Từ (1), (2) suy ra nghiệm của phương trình là \(\left[{}\begin{matrix}x=1\\x=5\end{matrix}\right.\)

D nha

đặt câu hỏi cho cụm từ nào bạn??? Mà chung chung thế này thì nhiều lắm

1. My brother prefers science fiction film to horror ones

2. It was not until 1925 that cinema became an industry

3. How many people were there at the concert last night

4. How often do you take a holiday

5. She went to school early to be on time

6. She wanted to buy a dictionary so that she went to the bookshop

7. It was not until midnight that he came home

8. It was not until she received his letter that she wrote to him

9. Tom turned on the radio to hear the football results

10. He gets up early not to be late

11. B. 12. A. 13. D

14. D. 15. C. 16. C.

17. B. 18. B. 19. B.

20. A

Lot

Câu này mk từng trả lời cho bạn r mà????

If I were you, I would be more truthful in the future

1. The most difficult

2. The most delighted

3. The most careful

4. The tallest

5. The best

1. As expensive as

2. As important as

3. As comfortable as

4. As good as

5. As bad as

6. As hard-working as

7. As good...as

8. As pretty as

9. As expensive as

10. As delicious as

Chọn gốc toạ độ là vị trí ném

Oy hướng lên; Ở phương ngang

Phương trình toạ độ:

x = vcosαt ≃ 7227 m

y = vsinαt + 1/2gt² ≃ 19141,3 m

1. More hard-working than

2. Better... than

3. Prettier than

4. More expensive than

5. More delicious than

6. More attractive than

7. Better than

8. Better than

9. More expensive than

10. More expensive than

1. More delicious

2. Larger

3. Cheaper

4. More expensive

5. More important

6. Happier

7. Stronger

8. More comfortable

9. Better

10. Worse