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1) thay m=1 vào 2 phương trình rồi được hệ 2 ẩn ...
2) Gọi hoành độ giao điểm là x, theo (p) thì ta có tung độ x²
Khi đó thay y = x² vào (d) ta có:
x²=(2m+2)x-m²-2m
<=>x²-2(m+2)x+2m+m²=0
Xét Delta'= (m+2)²-2m-m²=1 >0
=> pt có nghiệm x1,x2 với mọi m:
x1=m+2-1=m+1
x2=m+2+1=m+3
Thay vào điều kiện đã cho :
2(m+1)+m+3=5 <=> m=0

Áp dụng bất đẳng thức Cô-si :

\(a\sqrt{3a\left(a+2b\right)}+b\sqrt{3b\left(b+2a\right)}\le a\cdot\frac{3a+a+2b}{2}+b\cdot\frac{3b+b+2a}{2}\)

\(=a\cdot\frac{4a+2b}{2}+b\cdot\frac{4b+2a}{2}\)

\(=a\left(2a+b\right)+b\left(2b+a\right)\)

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

\(=2\left(a^2+b^2+ab\right)\le2\left(2+\frac{a^2+b^2}{2}\right)=2\left(2+\frac{2}{2}\right)=6\)

Dấu "=" xảy ra \(\Leftrightarrow a=b=1\)

p/s: có gì chiều giải nốt, giờ đi ăn cơm @@

Read the following passage, then choose the correct answer to questions 31 – 35.

Smoking causes lung cancer, which is the number one cancer among men. Ninety percent of the people who get lung cancer die. Smoking is also the leading cause of mouth cancer, tongue cancer, and throat cancer.Many smokers have heart disease and pneumonia. Smoking causes one million early deaths in the world every year.

Smokers not only harm themselves but also harm others. Smokers breathe smoke out into the air. They breathe it out on their children and their wives or husbands. Children whose parents smoke have more breathing and lung problems than other children. Women who are married to smokers are more likely to have lung cancer than those married to non-smokers.

We are all aware that smoking is bad. So why do people smoke?

31. The number one cancer among men is____________.

A. tongue cancer B. throat cancer C. lung cancer D. mouth cancer

32. The main cause of mouth cancer, tongue cancer and throat cancer is__________.

A. drinking B. overeating C. breathing D. smoking

33. Every year, smoking causes about one million____________.

A. cancer patients B. killing diseases C. early deaths D. injured men

34. The word “it” in the passage refers to____________.

A. cancer B. smoke C. air D. breath

35. Who are more likely to have lung cancer and lung problems?

A. People who live in the city B. People who live with smokers.

C. People who live with non-smokers. D. People who live in the country.

Complete the second sentence so that it has a similar meaning to the first one.

36. It’s 3 years since I last saw Nam.

– I haven’t seen Nam for 3 years.
37. “Don’t make so much noise, Peter.” said Carol

- Carol told Peter not to make so much noise.

38. Keeping the environment clean is very important.

- It’s very important to keep the environment clean.

39. “You should turn off the lights before going out”. Mrs. Hoa said.

- Mrs. Hoa suggested turning off the lights before going out/ (that) we (should) turn off the lights ...

40. Why don’t you plant some trees around your house to get more fresh air?

- How about planting some trees around your house to get more fresh air?

Read the following passage, then choose the correct answer to questions 26 – 30.

Jeans are very popular with (26)________people all over the world. Some people say that jeans are the “uniform” of youth. But they haven’t always been popular. The story of jeans (27)________almost two hundred years ago. People in Genoa, Italy made pants. The cloth made in genoa was (28)________“jeanos”. The pants were called “jeans”. In 1850, a saleman in California began selling pants made of canvas. His name was Levi Strauss. Because they were so strong, “Levi’s pants” became (29)________with gold miners, farmers and cowboys. Six years later Levis began making his pants with blue cotton cloth called denim. Soon after, factory (30)________in the US and Europe began wearing jeans. Young people usually didn’t wear them.

26. A. rich B. old C. young D. poor

27. A. start B. starts C. was starting D. started

28. A. call B. calls C. calling D. called

29. A. famous B. popular C. good D. wonderful

30. A. workers B. drivers C. cowboys D. farmers

1. Your dress is different from mine

-> My dress isn't ................the same your dress...........

2. Have you got a cheaper school bag than this?

-> Is this ..............cheapest school bag you have ?...........................

3. He often participates in outdoor activities during his summer vacation

-> He often takes ............part in outdoor activities during his summer vacation ..................

4. Who does this book belongto?

-> Who is ...........the owner of this book ?....................

5. My sisterr took two aspririns and then she ffelt a lot better

-> After .........taking 2 asprinrins , my sister felt a lot better ...........................

6. They intend to invite him to the party this weekend

-> they are ....going to invite him to the party this weekend.............................

7. He can't speak. He can't hear, either

-> He can ..........not speak nor hear..................

8. My aunt gave me some money this morning

-> I received .............some money from my aunt this morning ..............

9. Is it necessarry for me to clean this table?

-> Do I ....have to clean this table ?...........................

10. Farmers don't have as many days off as students

-> Farmers have .........fewer days off than students..............

Viết lại câu câu nghĩa tương đương

1. Your dress is different from mine

-> My dress isn't ...the same your dress......

2. Have you got a cheaper school bag than this?

-> Is this ...cheapest school bag you have ?......

3. He often participates in outdoor activities during his summer vacation

-> He often takes ...part in outdoor activities during his summer vacation .....

4. Who does this book belongto?

-> Who is ..the owner of this book ?......

5. My sisterr took two aspririns and then sshe ffelt a lot better

-> After ...talking two asprinrins , my sister felt a lot better .........

6. They intend to invite him to the party this weekend

-> They are... going to invite him to the party this weekend ........

7. He can't speak. He can't hear, either

-> He can.not speak nor hear ...........

8. My aunt gave me some money this morning

-> I received ...some money from my aunt this morning........

9. Is it necessarry for me to clean this table?

-> Do I ..have to clean this table?...............

10. Farmers don't have as many days off as students

-> Farmers have ...fewer days off than students............

Lời giải:

1. Khi $m=1$ thì PTĐT $(d): y=4$

PT hoành độ giao điểm:

$y=x^2=4\Rightarrow x=\pm 2$

Vậy tọa độ giao điểm của $(P)$ và $(d)$ là $(2;4); (-2;4)$

2.

PT hoành độ giao điểm:

$y=x^2-[2(m-1)x-m^2+5]=0$

$\Leftrightarrow x^2-2(m-1)x+m^2-5=0(*)$

Để $(d)$ tiếp xúc với $(P)$ thì PT $(*)$ chỉ có 1 nghiệm duy nhất.

Điều này xảy ra khi $\Delta'_{(*)}=(m-1)^2-(m^2-5)=0$

$\Leftrightarrow m=3$

3. Để $(P)$ và $(d)$ cắt nhau ở 2 điểm phân biệt thì PT $(*)$ phải có 2 nghiệm $x_1,x_2$ phân biệt.

Điều này xảy ra khi $\Delta'_{(*)}>0$

$\Leftrightarrow -2m+6>0\Leftrightarrow m< 3(*)$

Áp dụng định lý Vi-et: \(\left\{\begin{matrix} x_1+x_2=2(m-1)\\ x_1x_2=m^2-5\end{matrix}\right.\)

Khi đó:

$x_1,x_2\neq 0$ (để phân thức có nghĩa) thì $m^2-5\neq 0(**)$

Để $\frac{1}{x_1}+\frac{1}{x_2}=2$

$\Leftrightarrow \frac{x_1+x_2}{x_1x_2}=2$

$\Leftrightarrow \frac{2(m-1)}{m^2-5}=2$

$\Rightarrow m^2-m-4=0$

$\Rightarrow m=\frac{1\pm \sqrt{17}}{2}$ (đều thỏa thỏa mãn với $(*); (**)$)

Vậy......

Giúp mình với nha

I. Word form:

Every .HOUSEHOLDS.. in my neighborhood has at least one TV set. (HOUSE)

II. Prepositions:

I couldn't meet Mary because she was .OUT.. .

III. Find and correct one mistake:

We work very hardly => HARD but we have fun working together.

IV. Rewrite:

1. Have you got a cheaper school bag than this?

Is this the cheapest school bag have you got?

2. Who does this book belong to?

Who is own this book?

3. They intend to invite him to the party this weekend.

They are going to invite him to the party this weekend.

4. Is it necessary for me to clean this table?

Do I need to clean this table?

I. Word form:

Every households in my neighborhood has at least one TV set.

II. Prepositions:

I couldn't meet Mary because she was .OUT.. .

III. Find and correct one mistake:

We work very hardly => hard but we have fun working together.

IV. Rewrite:

1. Have you got a cheaper school bag than this?

\(\rightarrow\)Is this the cheapest school bag have you got?

2. Who does this book belong to?

\(\rightarrow\)Who is own this book?

3. They intend to invite him to the party this weekend.

\(\rightarrow\)They are going to invite him to the party this weekend.

4. Is it necessary for me to clean this table?

\(\rightarrow\)Do I need to clean this table?

do win catch go read speak get ".
1. Last month I...read.. an interesting book about Martin Luther King.
2. Janine....went.... to New York for two weeks last year.
3. She...spoke.. to her mother on the phone every day.
4.we...caught....three salmon in the river last weekend.
5. I..did.. some of my homework before breakfast this morning.
6. My cousin...got... a job at the new. Supermarket yesterday.
7. Our team ...won.... the school basketball competition last Saturday Bài tập 2: dịch and complete the sentences and questions with the past simple form of the verbs in brackets. Use the affirmative, negative or interrogative forms.
1.....did you write..( you/ write) an email to James last night?
2. I.....bought...(buy) the English-English dictionary because it was very expensive.
3....did Stuart see.. (Stuart/see) Karen yesterday evening? She wanted to speak to him.
4. We...went.( go) to the cinema last Friday, but the film was terrible!
5. Mum..cooked...(cook) dinner last night. We went to a restaurant instead.
6. I don't want lunch today because I ...had..( have) a big breakfast this morning.
7. ( you/go)did you go to the film club last Wednesday?

1.Dịch and complete the sentences. Use the past simple form of the verbs below. " do win catch go read speak get ". 1. Last month I..... an interesting book about Martin Luther King.

=> read

2. Janine........ to New York for two weeks last year.

went

3. She..... to her mother on the phone every day.

talks

4.we.......three salmon in the river last weekend.

=> caught

5. I.... some of my homework before breakfast this morning.

finished

6. My cousin...... a job at the new.

supermarket yesterday.

=> got

7. Our team ....... the school basketball competition last Saturday

=> won

Bài tập 2: dịch and complete the sentences and questions with the past simple form of the verbs in brackets.

Use the affirmative, negative or interrogative forms.

1.......( you/ write) an email to James last night?

=.> did you write

2. I........(buy) the English-English dictionary because it was very expensive.

=> didn't buy

3...... (Stuart/see) Karen yesterday evening?

Did stuart see

She wanted to speak to him.

4. We....( go) to the cinema last Friday, but the film was terrible!

went

5. Mum.....(cook) dinner last night. We went to a restaurant instead.

didn't cook

6. I don't want lunch today because I .....( have) a big breakfast this morning.

had

7. ( you/go) to the film club last Wednesday?

Did you do

+ với x = 3 ta có :

\(A=\frac{\sqrt{3}+4}{\sqrt{3}+2}=\frac{5\sqrt{3}+10-4\sqrt{3}-6}{\sqrt{3}+2}\) \(=\frac{5\left(\sqrt{3}+2\right)-2\sqrt{3}\left(\sqrt{3}+2\right)}{\sqrt{3}+2}\)

\(=\frac{\left(5-2\sqrt{3}\right)\left(\sqrt{3}+2\right)}{\sqrt{3}+2}=5-2\sqrt{3}\)

\(A=\frac{\sqrt{3}+4}{\sqrt{3}+2}\)

\(A=\frac{\sqrt{3}+2}{\sqrt{3}+2}+\frac{2}{\sqrt{3}+2}\)

\(A=1+\frac{2}{\sqrt{3}+2}\)

\(A=1+\frac{2\left(2-\sqrt{3}\right)}{\left(\sqrt{3}+2\right)\left(2-\sqrt{3}\right)}\)

\(A=1+\frac{4-2\sqrt{3}}{4-3}\)

\(A=1+4-2\sqrt{3}\)

\(A=5-2\sqrt{3}\)

1 . There is between written EL and spoken difference

2. the story of Oliver Twist moved us deeply

3 he tried to learn EL but he was unsuccessful

4 the machine is old , but it is useful

5 I" ll help you to some flowers choice.

6 what does this wedding ring symbolize

7 My brother play tennis verry  well

8 They look at the exam happily

9 I have not had such an evening enjoyment

10 I missed the of the play ending

Chúc bạn học tốt

ko phải thầy cô có được ko

với x>0,x≠16

1. He tried to learn Chinese but he was unsuccessfully( success)

2. He will never forget his happy childhood ( child)

3. How is your grandfather?- He is much better (well)

4. I watch TV everyday because it is very informative (inforrm)

5. We must keep our environment unpolluted( pollute)

6. They canceled all the filghts because of the fog (fly)

7. I'm going to the shop for a rice cooker . What brand do you recommend? (cook)

8. Every households in my neighborhood has at least on TV set ( house)

9. I can do all these exercises easily (easy)

10. His pronunciation of some words is not correct ( pronounce)

Tóm tắt:

U₁₂=U₁=U₂=6V

R₁=12Ω

R₂= 8Ω

ρ= 1,10.10^-6 Ω.m

U= 9V

a) Vẽ sơ đồ mạch điện? R_b=?

b) d=0,8mm=8.10^-4m

R_bm=15R_b :1= ?

Giải:

a) Sơ đồ mạch điện:

Vì U₁=U₂=6V < U=9V nên hai đèn Đ₁ và Đ₂ phải mắc song song với nhau và nối tiếp với biến trở R_b như hình trên.

Từ hình trên, để hai đèn sáng bình thường ta có:

\(I_1=\frac{U1}{R1}=\frac{6}{12}=0,5A\)

\(I_2=\frac{U2}{R2}=\frac{6}{8}=0,75A\)

U_b= U-U₁₂=9-6=3V

I_b= I₁+I₂= 0,5+0,75= 1,25A

Gía trị R_b của biến trở khi hai đèn sáng bình thường là

Rb= \(\frac{U_b}{I_b}=\frac{3}{1,25}=2,4\Omega\)

b) Gía trị lớn nhất là R_bm= 15R_b =15.2,4=36Ω

Áp dụng CT: R_bm= ρ\(\frac{1}{S}=\rho\frac{1}{\pi\left(\frac{d}{2}\right)^2}\)

Độ dài tổng cộng 1 của dây quấn biến trở nói trên là:

1=\(\frac{\pi.R_{bm}}{4\rho}.d^2_1=\frac{3,14.36}{4.1,1.10^{-6}}.\left(8.10^{-4}\right)^2\approx16,44m\)

a) Xét \(\Delta ABI\) và \(\Delta AMI\) ,có :

AI : cạnh chung

AB = AM ( gt )

\(\widehat{BAI}=\widehat{MAI}\) ( AI là tia p/g của góc A )

=> \(\Delta BAI=\Delta MAI\left(c.g.c\right)\)

=> BI = MI

b) Xét \(\Delta ABH\) vuông tại H :

AB > AH

Mà AB = AM

=> AM > AH

c) IC > IM

mà IM = IB

=> IC > IB

d) AM = AB

=> \(\Delta AMB\) cân tại A

=> AI là tia p/g đồng thời là đường cao của \(\Delta AMB\)

=> AI \(\perp BM\)

a)Do tam giác ABC cân ở A và AH là đường cao

=>AH là trung tuyến tại đỉnh A

=>H là trung điểm BC

=>BH=\(\dfrac{1}{2}\)BC=3(cm)

Áp dụng định lí pytago cho tam giác vuông AHB

AB²=AH²+HB²

=>AH²=AB²-HB²=5²-3²=16

=>AH=4(cm)

b)G là trọng tâm tam giác ABC => G nằm trên trung tuyến kẻ từ đỉnh A

Theo câu a: AH là trung tuyến kẻ từ A

=>A,H,G thẳng hàng

c)Do tam giác ABC cân ở A và AH là đường cao=>AH là đường phân giác=>\(\widehat{CAG}=\widehat{BAG}\)

Tam giác ABC cân ở A=>AB=AC

Xét tam giác ABG và tam giác ACG có:

AB=AC

\(\widehat{CAG}=\widehat{BAG}\)

AG chung

=>\(\Delta ABG=\Delta ACG\)(C.G.C)

=>\(\widehat{ABG}=\widehat{ACG}\)(góc tương ứng)