=) check in vs out như nào ah=')

Tổng số phần trăm học sinh đạt điểm giỏi và khá là: 25% + 55% = 80%

Số học sinh đạt điểm trung bình chiếm: 100% - 80% = 20%

Hiệu số phần trăm giữa học sinh khá và giỏi là: 55% - 25% = 30%

30% số học sinh của lớp tương ứng với 12 học sinh, vậy tổng số học sinh của lớp là:

\(\dfrac{12}{30\%}\) . 100% = 40 (học sinh)

Số học sinh đạt điểm giỏi là: 40 . 25% = 10 (học sinh)

Số học sinh đạt điểm khá là: 40 . 55% = 22 (học sinh)

Số học sinh đạt điểm trung bình là: 40 . 20% = 8 (học sinh)

IX. Choose the correct answers.
1. ‘There was an accident outside the supermarket.’
A. He said there had been an accident outside the supermarket.
B. He said there was an accident outside the supermarket.
C. He said there has been an accident outside the supermarket.
2. ‘Have you ever seen a UFO?’
A. Jim wanted to know if had I ever seen a UFO.

B. Jim asked if I had ever seen a UFO.
C. Jim asked whether I ever saw a UFO.
3. She asked if you’d seen her painting on display in the exhibit.
A. ‘Will you see my painting on display in the exhibit?’
B. ‘Did you see my painting on display in the exhibit?’
C. ‘Have you seen her painting on display in the exhibit?’
4. I’m flying to India tomorrow.’
A. Yesterday, Matt said that he was flying to India tomorrow.
B. Yesterday, Matt told me that I was flying to India the next day.

C. Yesterday, Matt said that he was flying to India the following day.

5. ‘Why did you go out last night?’
A. She asked me why I had gone out the night before.
B. She asked me why did I go out the previous night.
C. She wanted to know why I went out that night.
6. My instructor said that we were the best class he’d ever taught.
A. ‘You are the best class I’ve ever taught,’ my instructor said.
B. ‘You were the best class I ever taught/ my instructor said to me.
C. ‘They are the best class he’s ever taught,’ said my instructor.
7. ‘Can you help me with my homework?’
A. Nick asked whether his sister can help him with his homework.
B. Nick asked his sister could she help him with his homework.
C. Nick asked his sister if she could help him with his homework.
8. Bill wanted to know when Susan was going out with Tony.
A. ‘When you are going out with Tony, Susan?’
B. ‘When was you going out with Tony, Susan?’
C. ‘When are you going out with Tony, Susan?’
9. ‘I will come if I can finish work early.’
A. He said that he will come if he can finish work early.
B. He told that he would come if he could finish work early.
C. He told me that he would come if he could finish work early.
10. ‘What is the closest planet to Earth?’
A. The student wondered if the closest planet to Earth is.
B. The student asked what the closest planet to Earth was.
C. The student asked what was the closest planet to Earth.

1.Tim said that he had been there three months before.

2. He wanted to know when the next train left.

3.She asked me if I was meeting Judy at four o’clock that day.

4.Jane told me that she had already seen that exhibition.

5. My mother asked who I had met at the party the night before.

6. Miki said that they were having dinner then, so she could only talk for a minute.

7. I asked Peter if I could use his phone.

8. The Prime Minister announced that public spending would be increased the following year.

9.Peter said that his father drank a cup of coffee every morning before going to work.

10. Cheryl asked the old woman how long she had lived there.

1 The woman asked John if/whether she might ask him a few questions.

2The teacher asked me if I had done my project about space exploration.

3 Debbie asked her father if they would be able to live on Mars in 2050.

4I asked the Browns whether they were having a barbecue that night.

5Jane asked Tom if he liked sci-fi films that feature extraterrestrial life.

6Val asked me whether scientists had found life on Mars many years ago.

7Many people wondered whether aliens or UFOs were real.

8Sally asked her best friend whether they could go to the National Museum the following day.

9 Duc asked Trang if she knew NASA had found two new planets.

10She wanted to know whether he had been there the previous day. 

1 Jane asked me where we would live in 20 years’ time.

2 I asked Peter how his trip to Toronto had been.

3Sue asked  why Judy hadn't waited for fireballs last night.  

4The teacher asked us how many planets there were in the solar system.

5Elliot wanted to know how many days it took to get to Mars from Earth.

6I asked Sally what she was staring at.

7Joe asked his teacher who had discovered the planet Neptune.

8He asked the astronaut how long she had been living on the International Space Station.

9The students wanted to know when humans would go to Venus.

10 I asked Sally and Andy where they were going this summer holidays.

a) \(\Delta\) ABC có

AB = AC (gt)

=> \(\Delta\) ABC cân tại A.

AD là đường cao của tam giác ABC (gt)

=> AD cũng là đường trung tuyến của tam giác ABC (tính chất tam giác cân).

=> BD = CD (đpcm).

b)Xét tam giác vuông ADH và tam giác vuông ADK:

AD là cạnh chung.

\(\widehat{HAD}=\widehat{KAD}\) (do AD là phân giác của \(\widehat{BAC}\)).

=> ΔADH = ΔADK (cạnh huyền - góc nhọn).

=> DH = DK (hai cạnh tương ứng) (đpcm).

c)\(\Delta\) ABC có AB = AC (gt) => Tam giác ABC cân tại A.

=> \(\widehat{ABC}=\widehat{ACB}\)(tính chất tam giác cân).

\(\Delta\) ADH có DH ⊥ AB => \(\widehat{AHD}\)= 90°.

\(\Delta\) ADK có DK ⊥ AC => \(\widehat{AKD}\) = 90°.

Xét \(\Delta\) AHK có:

AH = AK (do ΔADH = ΔADK).

=> Tam giác AHK cân tại A.

=> \(\widehat{AHK}=\widehat{AKH}\)

Mà \(\widehat{AHK}+\widehat{BHD}\) = 180° (kề bù).

\(\widehat{AKH}+\widehat{CKD}\) = 180° (kề bù).

Mặt khác, \(\widehat{BHD}=\widehat{CKD}\) (cùng phụ với \(\widehat{BAD}\)).

=> \(\widehat{AHK}=\widehat{AKH}=\widehat{ABC}=\widehat{ACB}\)

 Xét tứ giác BCHK có:

\(\widehat{AHK}=\widehat{ABC}\) (cmt)

Mà hai góc này ở vị trí đồng vị.

 => HK // BC (đpcm).

Để \(2\sqrt{C}-1<0\) ta cần:

\(2\sqrt{C} < 1\)

\(\sqrt{C} < \frac{1}{2}\)

\(C < \frac{1}{4} \) do \(C ≥ 0\)

Thay \(C=\frac{\sqrt{x}-2}{\sqrt{x}+1}\) vào, ta được:

\(\frac{\sqrt{x}-2}{\sqrt{x}+1} < \frac{1}{4}\)

Vì \(\sqrt{x}+1 > 0\) với mọi \(x\ge 0 \)

=> \(4(\sqrt{x}-2) < \sqrt{x}+1\)

\(4\sqrt{x}-8 < \sqrt{x}+1\)

\(3\sqrt{x} < 9\)

\(\sqrt{x} < 3\)

\(x < 9\)

\(0 \le x < 9\)

Vậy, các giá trị của x để \(2\sqrt{C}-1<0\) là \(0 \le x < 9\)

Gọi số tiền của Linh là x (đồng) và số tiền của Anh là y (đồng).

Theo đề bài, ta có :

Tổng số tiền lì xì của hai bạn:

x+y=1,000,000 đồng

Số tiền của Anh lớn hơn số tiền của Linh 100 nghìn đồng:

y=x+100,000

Thay phương trình thứ hai vào phương trình đầu tiên:

x+(x+100,000)=1,000,000

2x+100,000=1,000,000 

2x=1,000,000−100,000

2x=900,000

x=450,000đ

Số tiền của Anh là:

y=x+100,000

=450,000+100,000

=550,000đ

Phương trình chuyển động:

Vật A: xA = vA . t = 6t

yA = 0

Vật B: xB = 0

yB = -100 + vB . t = -100 + 2t

Khoảng cách giữa hai vật:

Gọi d là khoảng cách giữa A và B tại thời điểm t.

Ta có: d² = (xA - xB)² + (yA - yB)² d²

= (6t)² + (0 - (-100 + 2t))² d²

= 36t² + (100 - 2t)² d²

= 36t² + 10000 - 400t + 4t² d²

= 40t² - 400t + 10000

Để d nhỏ nhất,cần tìm giá trị nhỏ nhất của biểu thức d² = 40t² - 400t +10000.

Hoành độ đỉnh của parabol là: t = \(\dfrac{-b}{2a}=-\dfrac{-400}{2.40}\) = 5 giây.

Thay t = 5 vào phương trình chuyển động của A và B:

xA = 6. 5 = 30 m

yB = -100 + 2 .5 = -90 m

Vậy:

Hai vật không gặp nhau.Khoảng cách nhỏ nhất giữa hai vật là khi t = 5 giây. Lúc đó, vật A ở (30, 0) và vật B ở (0, -90).