Talk about a city you want to visit
a. Where is it? b. What do you know about this city? c. How do you go there? d. When do you want to visit there? e. Why do you want to visit it?
Câu 1:
1) Thay x=16 vào N, ta được:
\(N=\dfrac{2\cdot\sqrt{16}+1}{3-\sqrt{16}}=\dfrac{2\cdot4+1}{3-4}=\dfrac{9}{-1}=-9\)
Vậy: Khi x=16 thì N=-9
Câu 2:
2) Ta có: \(M=\dfrac{2\sqrt{x}-9}{x-5\sqrt{x}+6}-\dfrac{\sqrt{x}+3}{\sqrt{x}-2}\)
\(=\dfrac{2\sqrt{x}-9}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}-\dfrac{\left(\sqrt{x}+3\right)\left(\sqrt{x}-3\right)}{\left(\sqrt{x}-3\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{2\sqrt{x}-9-x+9}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)
\(=\dfrac{-x+2\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)
\(=\dfrac{-\sqrt{x}\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-3\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{-\sqrt{x}}{\sqrt{x}-3}\)
Câu 2 :
Gọi : vận tốc của người đi chậm là : x (km/h) ( x > 0 )
Vận tốc của người đi nhanh : x + 4 (km/h)
Vi : người đi chậm đến muộn hơn : 45 phút \(=\dfrac{3}{4}\left(h\right)\)
Khi đó :
\(\dfrac{36}{x}-\dfrac{36}{x+4}=\dfrac{3}{4}\)
\(\Leftrightarrow\left[36\cdot\left(x+4\right)-36x\right]\cdot4=3x\cdot\left(x+4\right)\)
\(\Leftrightarrow3x^2+12x-144=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=12\left(n\right)\\x=16\left(l\right)\end{matrix}\right.\)
Hello everyone. Do you know anything about London? Today, I'll tell you about it.
The weather in here is cold and little sunshine. The people in here are friendly. When you have a trouble, they always help you. Big Ben is the famous tower in England. The London Eye is the tallest observation wheel in the world and each rotation takes about 30 minutes. You can see nice view of London. In here, there are many ancient buildings. It has from the last centuries.
This is my favorite cit. It is beautiful and romantic city. Thanks for listening! ヾ(•ω•`)o
4 They haven't cleaned their room for 2 weeks
5 John last had his hair cut over six months ago
6 When did you ride a bicycle?
7 When did he write to you?
8 How long is it since he last talked to you?
9 How long is it since you last telephoned him?
10 It's the first time I have never eaten this kind of food
11 I have never seen this film before
12 He hasn't gone abroad before
13 She has driven for 1 month
14 We have eaten since it started to rain
15 I haven't had my hair cut sinve I left her