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ai giúp mk vs ạ
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giúp mk vs ạ ai nhanh mk tick nha
19 tháng 4 2022
a. xét tam giác ABC và tam giác BHC có:
góc B = góc C = 90o
góc C chung
=> tam giác ABC ~ tam giác BHC (g.g)
Áp dụng định lí Pytago vào tam giác ABC, ta có:
AB2+BC2=AC2
36 + 64= AC2
AC2= 100
AC= 10 (cm)
vì tam giác ABC ~ tam giác BHC
=> \(\dfrac{AB}{BH}\)= \(\dfrac{AC}{BC}\)
=> BH = \(\dfrac{AB.BC}{AC}\)
=> BH= \(\dfrac{6.8}{10}\)= 4,8 (cm)
19 tháng 4 2022
gọi số học sinh mua vở dự kiến là x
số học sinh mua vở trong quá trình thực hiện là x - 15
Theo đề ta có:
5x + 691= 6(x-15)
5x + 691= 6x - 90
5x - 6x = -90 - 691
-x= -781
x= 781
vậy trường có 781 học sinh.
19 tháng 4 2022
a.\(ĐK:x\ne\pm1;x\ne-\dfrac{1}{2}\)
\(P=\left(\dfrac{x}{x+1}-\dfrac{x+1}{x-1}+\dfrac{7x-3}{x^2-1}\right):\dfrac{4}{2x+1}\)
\(P=\left(\dfrac{x\left(x-1\right)-\left(x+1\right)\left(x+1\right)+7x-3}{\left(x-1\right)\left(x+1\right)}\right):\dfrac{4}{2x+1}\)
\(P=\dfrac{x^2-x-x^2-2x-1+7x-3}{\left(x-1\right)\left(x+1\right)}.\dfrac{2x+1}{4}\)
\(P=\dfrac{\left(4x-4\right)\left(2x+1\right)}{4\left(x-1\right)\left(x+1\right)}\)
\(P=\dfrac{4\left(x-1\right)\left(2x+1\right)}{4\left(x-1\right)\left(x+1\right)}\)
\(P=\dfrac{2x+1}{x+1}\)
b.\(2x^2+x=0\)
\(\Leftrightarrow x\left(2x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\left(tm\right)\\x=-\dfrac{1}{2}\left(ktm\right)\end{matrix}\right.\) ( vì \(x\ne-\dfrac{1}{2}\) )
\(x=0\Leftrightarrow P=\dfrac{2.0+1}{0+1}=\dfrac{1}{1}=1\)
21 tháng 4 2021
1. He met many friends who encouraged him in his work.
2. He often tells me about the village where he was born.
3. Can you understand the question which he asked you last time?
4. The man whose son we play with every day is an architect.
5. The city where we spent our vacation was very beautiful.
6. The train which arrived two hours late broke down twice on the way.
7. I stopped in a smal ltown where my sister is working.
8. The book which I gave him was rather difficult.
9. The picture which you were talking about has been stolen.
10. She is the girl who I bought these roses for.
11. This morning I met Diana who I hadn't seen for ages.
12. Tulip computers which are made in Holland are very good.
13. I saw a girl whose beauty took my breath away.
14. John, whose mother is in hospital, is absent from school.
DT
Đỗ Thanh Hải
CTVVIP
21 tháng 4 2021
1 Was that house built in 1972
2 I wasn't invited to the birthday party
3 She will be given a prize by the teacher if she works well
4 He was said to be able to swim across this river
5 You were showed the way to Thule Zoo by the police
6 I won't be told the truth about the situation by him
7 The valley can be seen from the top of this hill
8 He was chosen the monitor by all the students
9 Your hand must be washed
10 Many matches haven't been won by my favorite football team so far this season
11 This bicycle has been used for 5 years by my father
12 Measures are being taken to attract foreign investment by the government
13 Her house was broken into last night
14 How is this amount of money spent by you?
15 Have any good films been seen by you so far?
16 How was your leg broken?
17 The postman is being attacked by my dog
DT
Đỗ Thanh Hải
CTVVIP
16 tháng 4 2021
II
1 is => was
2 am => were
3 play => playing
4 good => well
5 is => were
6 didn't => hasn't
7 to get => getting
8 can => could
9 serious => seriously
10 which => who
DT
Đỗ Thanh Hải
CTVVIP
30 tháng 4 2021
1 would invite
2 sold
3 would buy
4 rains
5 is
6 could pass
7 repaired
8 will help
9 will do
10 learn
11 will have
12 looked
13 fed
14 would understand
15 would arrive
16 wouldn't have had
17 swim
18 press
19 asked
20 would call
21 cycle
22 will miss
23 had
24 woud support
25 will phone
DT
Đỗ Thanh Hải
CTVVIP
30 tháng 4 2021
26 goes
27 parked
28 don't wear
29 will get
30 will turn
31 go
32 didn't rain
33 wore
34 would watch
35 had signed
36 would live
37 switched off
38 would understand
39 had explained
40 would have arrived
41 won't play
42 grew
43 would see
44 didn't have to do
45 hadn't stayed up
46 wait
47 would miss
48 would have help
49 had used
50 would be
xl mk lop 5