mấy bn có ai có đáp án đề đề nghị tiếng anh lớp 7 của trường Nguyễn Khuyến, Cao Thắng, Nguyễn Đình Chiểu, Lương Thế Vinh, Trần Phú ko cho mk xin vs!
Cảm ơn nhìu!
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NH
5
16 tháng 5 2021
Bài 1 :
a, Ta có : \(x=4\Rightarrow\sqrt{x}=2\)
Thay vào biểu thức A ta được :
\(A=\frac{2+4}{4+4}=\frac{6}{8}=\frac{3}{4}\)
b, \(x\ge0;x\ne16\)
\(B=\frac{x}{x-16}-\frac{2}{\sqrt{x}-4}-\frac{2}{\sqrt{x}+4}\)
\(=\frac{x-2\sqrt{x}-8-2\sqrt{x}+8}{x-16}=\frac{x-4\sqrt{x}}{x-16}\)
\(=\frac{\sqrt{x}\left(\sqrt{x}-4\right)}{\left(\sqrt{x}\pm4\right)}=\frac{\sqrt{x}}{\sqrt{x}+4}\)
c, Ta có : \(C=A.B=\frac{\sqrt{x}}{\sqrt{x}+4}.\frac{\sqrt{x}+4}{x+4}=\frac{\sqrt{x}}{x+4}\le0\)
Dấu ''='' xảy ra khi \(x=0\)( em ko chắc ý c lắm vì cũng chưa gặp bh )
trình bày như này thì khi thế x vào mẫu nó là 0 nên băn khoăn :)
\(x+4\le0\)do \(\sqrt{x}\ge0\)\(\Leftrightarrow x\le-4\)
PN
16 tháng 5 2021
Ta dễ thấy điểm rơi đạt tại \(x=2;y=3;z=4\)
Áp dụng bất đẳng thức AM-GM :
\(A=\left(\frac{3}{x}+\frac{3x}{4}\right)+\left(\frac{9}{2y}+\frac{y}{2}\right)+\left(\frac{4}{z}+\frac{z}{4}\right)+\frac{1}{4}\left(x+2y+3z\right)\)
\(\ge2\left(\frac{3}{2}+\frac{3}{2}+1\right)+\frac{1}{4}.20=13\)
Vậy Min A = 13 <=> x = 2 ; y = 3 ; z = 4
H
1
T
1 tháng 4 2021
ĐỀ LUYỆN THI IOE LỚP 5
1. house / is / the city. / in / My
...............................................................................
2. Peter / go / on foot? / Does / to work
................................................................................
3. _ESULT
4. My mother gave me a _ _ _ _ _ _ _ yesterday.
5. We have English on Tuesday and Saturday. We have it ... a week.
A. once B. twice
C. two times D. three times
6. Go straight and Mai's house is ... your right.
A. at B. in
C. beside D. on
7. a shower / You should / take / twice / a week.
....................................................................................
8. an / orange. / is / That
..................................................
9. My father sometimes plays _ _ _ _ _ _ with his friends.
10. Remember to drink water everyday. It's good _ _ _ our health.
11. Choose the odd one:
A. sing B. play
C. draw D. yesterday
12. Make ... circles.
A. four B. a
C. for D. one
13. is / chicken. / favorite / My / food
.................................................................................
14. frogs / some / garden. / There are / in the
..................................................................................
15. I want to be a musician in _ _ _ future.
16. All of my friends watching cartoons _ _ TV.
17. She s going ... in the fall.
A. fish B. fishing
C. fishes D. to fish
18. Where is my cup of tea? – It's ... the kitchen.
A. in front of B. under
C. behind D. in
19. interesting / doing / We are / things. / many
...............................................................................
20. to school / I / usually / go / by bike.
................................................................................
21. Happy birthday to y_ _!
22. What subject are you good _ _ , Elisa?
23. I have ... on Monday. I the subject very much.
A. biology B. novel
C. education D. science
24. Choose the word that has the underlined part pronounced differently:
A. hour B. house
C. hen D. hot
25. to learn / many interesting things / I / about animals. / love
......................................................................................
26. usually / play / Trinh and Thang / table tennis / together.
.........................................................................................
27. We are having _ break now.
28. There are many cows in the _ _ _ _ _ _ _ of my family.
29. Hoa was very surprised when she looked at ... in the mirror.
A. she B. hers
C. herself D. her
30. Choose the word that has the underlined part pronounced differently from the others:
A. season B. weather
C. week D. beach
31. activities in / a lot of / interesting / There are / the festival.
.....................................................................................
32. has / and / a son. / a daughter / Mrs Hanh
.......................................................................................
33. Don't forget to post the letter _ _ _ me.
34. After dinner, my mother checks my homework b_ _ _ _ _ bedtime.
35. I ... born on November 17th.
A. was B. were
C. am D. is
BT
5
Rất tiếc là mk chỉ có đáp án của LTV, NK và TP thôi
nhưng mà mk thi xong rồi! ko cần đâu Thanks