a) ∠CEz + ∠zEy' = 180⁰ (kề bù)

⇒ ∠CEz = 180⁰ - ∠zEy'

= 180⁰ - 120⁰

= 60⁰

⇒ ∠CEz = ∠xDz = 60⁰

Mà ∠CEz và ∠xDz là hai góc đồng vị

⇒ xx' // yy'

b) Do HC ⊥ xx' (gt)

xx' // yy' (cmt)

⇒ HC ⊥ yy'

c) Do HC ⊥ yy' (cmt)

⇒ ∠HCy = 90⁰

⇒ ∠BCy = ∠HCy - ∠BCH

= 90⁰ - 40⁰

= 50⁰

c) Vẽ tia Bt // xx'//yy'

⇒ ∠CBt = ∠BCy = 50⁰ (so le trong)

⇒ ∠ABt = ∠ABC - ∠CBt

= 90⁰ - 50⁰

= 40⁰

Do Bt // xx'

⇒ ∠xAB = ∠ABt = 40⁰ (so le trong)

Ta có:

∠BAx' + ∠xAB = 180⁰ (kề bù)

⇒ ∠BAx' = 180⁰ - ∠xAB

= 180⁰ - 40⁰

= 140⁰

e) Do AB cắt tia Bt tại B

Mà Bt // yy'

⇒ AB cắt yy'

Được kẻ thêm tia nhé mn

a, Diện tích khu vườn  hình thang là:

\(\left(60+80\right)\times50:2=3500m^2\)

b, Diện tích bồn đất trồng hoa là:

\(18\times25=450m^2\)

c,Ta có: \(450=200.2+50\)

Vậy cần ít nhất 3 túi giống rau để gieo hết phần đất trồng rau.

đâu

ai đó giúp tui zới

\(A^3_n+5A^2_n=2\left(n+15\right)\)

ĐK: n ≥ 3 (n∈N)

<=> \(\dfrac{n!}{\left(n-3\right)!}+\dfrac{5.n!}{\left(n-2\right)!}=2\left(n+15\right)\)

<=> \(\dfrac{n\left(n-1\right)\left(n-2\right)\left(n-3\right)!}{\left(n-3\right)!}+\dfrac{5n\left(n-1\right)\left(n-2\right)!}{\left(n-2\right)!}=2\left(n+15\right)\)

<=> \(n\left(n-1\right)\left(n-2\right)+5\left(n-1\right)n-2n-30=0\)

<=> \(n^3+2n^2-5n-30=0\) <=> n=3

đâu

câu hỏi đâu ?????????????

Để hệ phương trình có nghiệm duy nhất thì \(\dfrac{m}{3}< >-\dfrac{1}{m}\)

=>\(m^2\ne-3\)(luôn đúng)

Ta có: \(\left\{{}\begin{matrix}mx-y=2\\3x+my=3m\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}y=mx-2\\3x+m\left(mx-2\right)=3m\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}y=mx-2\\3x+m^2x-2m=3m\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}y=mx-2\\x\left(m^2+3\right)=5m\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{5m}{m^2+3}\\y=m\cdot\dfrac{5m}{m^2+3}-2\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x=\dfrac{5m}{m^2+3}\\y=\dfrac{5m^2-2m^2-6}{m^2+3}=\dfrac{3m^2-6}{m^2+3}\end{matrix}\right.\)

\(\left(x+y\right)\cdot\left(m^2+3\right)+8=0\)

=>\(\dfrac{5m+3m^2-6}{m^2+3}\cdot\left(m^2+3\right)+8=0\)

=>\(3m^2+5m-6+8=0\)

=>\(3m^2+5m+2=0\)

=>(m+1)(3m+2)=0

=>\(\left[{}\begin{matrix}m=-1\\m=-\dfrac{2}{3}\end{matrix}\right.\)

Bài 2:

Thay x=-1 vào (P), ta được:

\(y=\left(-1\right)^2=1\)

Thay x=2 vào (P), ta được:

\(y=2^2=4\)

vậy: A(-1;1); B(2;4)

Gọi (d): y=ax+b(a\(\ne\)0) là phương trình đường thẳng AB

Thay x=-1 và y=1 vào (d), ta được:

\(a\cdot\left(-1\right)+b=1\)

=>-a+b=1(1)

Thay x=2 và y=4 vào (d), ta được:

\(2\cdot a+b=4\)

=>2a+b=4(2)

Từ (1) và (2) ta có hệ phương trình: \(\left\{{}\begin{matrix}-a+b=1\\2a+b=4\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}-3a=-3\\-a+b=1\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}a=1\\b=a+1=1+1=2\end{matrix}\right.\)

Vậy: phương trình AB là y=x+2

d: \(=\dfrac{-9\sqrt{3}-6\sqrt{2}}{19}-\dfrac{\sqrt{3}}{5}\)

\(=\dfrac{-64\sqrt{3}-30\sqrt{2}}{95}\)

b: \(=\dfrac{37\left(7-2\sqrt{3}\right)}{49-12}=7-2\sqrt{3}\)

Có vẽ hình nha mn

Bài 6:

I. Phonics:

Odd one out:

Odd one out:

II. Vocabulary:

Odd one out:

Choose the correct answer:

16. What would you to be in the future? – I’d to be _____ writer.

A. a

B. an

C. Ø

D. the

17. I think Tam is _______.

A. greedy

B. kind

C. ugly

D. stupid

18. My favourite book is _______.

A. comics

B. songs

C. TV

D. children

19. The main character in Snow White is _______.

A. the princess

B. Snow White

C. Doraemon

D. Tom

20. Trung would to be a _______ in the future.

A. pilot

B. engineer

C. artist

D. architect

21. What are you doing? – I am _______ my favourite books.

A. read

B. reading

C. listen

D. listening

22. Nam has a high temperature. He has a/an _______.

A. earache

B. stomachache

C. fever

D. toothache

23. Why do you would to be a teacher? - _______ I’d to teach children.

A. When

B. Because

C. What

D. Where

24. Why would you to be a nurse? - _______.

A. Because I would to look after the patients.

B. Because I would to teach the children.

C. Because I would to write stories for children.

D. Because I would to fly a plane.

25. Linda has a pain in her throat. She has a/an _______.

A. toothache

B. sore throat

C. earache

D. backache

26. Don’t ride your _____ so fast!

A. car

B. matches

C. bike

D. stairs

27. You shouldn’t play with the knife because it’s _______.

A. small

B. sharp

C. tall

D. deep

28. What is she doing? – She _______ with matches.

A. are playing

B. was playing

C. is playing

D. am playing

29. What’s the ______ with you, Tony? – I’ve got a fever.

A. problem

B. matter

C. happiness

D. luck

30. What do you do in your free time? – I surf _______.

A. the Internet

B. comics

C. homework

D. flowers

31. John is riding his bike _______ the park.

A. on

B. at

C. above

D. in

32. I love karate. I _______ karate every day.

A. work

B. make

C. do

D. clean

33. Hoa often _______ to the music club every Sunday.

A. goes

B. does

C. listens

D. climbs

34. They _______ and singing songs.

A. dancing

B. climbing

C. going

D. doing

35. A: Thanks for your lovely gift.

B: ________.

A. You’re welcome 

B. Go ahead!

C. I’m sorry!

D. Don’t worry about it!

36. Quan has a pain in his stomach. He has a/an _______.

A. toothache

B. stomach ache

C. sore throat

D. headache

III. READING

Task 1. Look and write the correct words.

Toothache/ bus stop/ pilot/ rice/ The story of Tam and Cam/

37. It’s a fairy tale about two sisters. ______________

38. He has a pain in her tooth. ________________

39. A person who flies or is qualified to fly an aircraft or spacecraft. ____________

40. A Southeast Asian grass widely grown in warm wet areas especially for its seeds which are used for food. _________________

41. A place where a bus regularly stops, usually marked by a sign. _________________

Task 3: Read and answer the questions.

Hi, I’m Mai. My hobby is reading folk tales. Folk tales are usually short and interesting. They often give me one surprise after another. The character are sometimes honest, sometimes greedy, sometimes wise, and sometimes stupid. I The Fox and the Crow very much. The Fox was clever and the Crow was not. The Crow lost its delicious meat and the Fox got it. I love folk tales very much because each of them gives me a lesson in life.

49. What kinds of stories does Mai reading?

____________________________________________________.

50. What does she think of folk tales?

____________________________________________________.

51. What does she think of the characters in folk tales?

____________________________________________________.

52. What does she think of the characters in The Fox and the Crow?

_________________________________________________

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