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2
16 tháng 8 2023
`a)` Vì `O` là trung điểm của `AC;BD`
`=>{(\vec{OA}=-\vec{OC}),(\vec{OB}=-\vec{OD}):}`
Ta có: `\vec{OA}+\vec{OB}+\vec{OC}+\vec{OD}`
`=-\vec{OC}-\vec{OD}+\vec{OC}+\vec{OD}=0`
`b)` Vì `E` là trung điểm `AD=>\vec{EA}=-\vec{ED}`
Ta có: `\vec{EA}+\vec{EB}+2\vec{EC}`
`=\vec{EA}+\vec{EA}+\vec{AB}+2\vec{ED}+2\vec{DC}`
`=-2\vec{ED}+\vec{AB}+2\vec{ED}+2\vec{AB}=3\vec{AB}`
`c)` Ta có: `\vec{EB}+2\vec{EA}+4\vec{ED}`
`=\vec{EB}-2\vec{ED}+4\vec{ED}`
`=\vec{EB}+2\vec{ED}`
`=\vec{EA}+\vec{AB}+2\vec{ED}`
`=-\vec{ED}+\vec{AB}+2\vec{ED}`
`=\vec{AB}+\vec{EC}+\vec{CD}` (Mà `\vec{AB}=-\vec{CD}`)
`=\vec{EC}`
TK
14 tháng 12 2021
Câu 2
Đổi : 72 km/h =20 m/s
Gia tốc của ô tô là
\(a=\dfrac{v^2-v_0^2}{2s}=\dfrac{20^2-4^2}{2\cdot400}=0,48\left(\dfrac{m}{s^2}\right)\)
Câu 3:
\(\dfrac{F_1}{F_2}=\dfrac{d_2}{d_1}\Rightarrow d_2=\dfrac{F_1\cdot d_1}{F_2}=\dfrac{30\cdot6}{40}=4,5\left(cm\right)\)
Khoảng cách giữa lực F1 và F2
\(d=d_1+d_2=6+4,5=10,5\left(cm\right)\)
10 tháng 10 2021
a: Thay x=2 và y=3 vào hàm số, ta được:
\(2k+2-4=3\)
\(\Leftrightarrow k=\dfrac{5}{2}\)
PK
3
SV
Sinh Viên NEU
CTVVIP
7 tháng 12 2023
62 The more I think about the idea, the less attractive it becomes
63 The more slowly you walk, the longer it takes to get there
64 The less right you treat your disease, the more increasingly serious it will become
65 câu này thiếu dữ liệu roài
66 The newer the motorbike is, the less petrol it consumes
67 The more electricity you use, the higher your bill will be
68 The more books he reads, the more he knows about the word
69 The more I thought about , the more confused I became
70 The more problems arise, the less enthusiastic we feel
SV
Sinh Viên NEU
CTVVIP
7 tháng 12 2023
71 The more polluted the air is, the greater the chances of developing respiratory diseases are
72 The more popular TV programs become, the worse they seem to get
73 The less my boss is pressed for time, the worse he works
74 The more the economy grows, the better people's living conditions become
75 If you go to bed late, you will be tired
76 Unless you spend all your money, we can go on holiday
77 If you don't study, you won't pass your exams
78 Unless he smokes, the house won't smell bad
79 If you don't put your clothes away, your room will bea mess
80 If you don't go shopping, there won't be any food in the fridge
AL
1 tháng 5 2021
Now, many people are aiming for a good life so they have moved to the city, which is fully furnished. So what are the prerequisites for a city to be liveable living? A city needs the following conditions. A city needs full convergence of factors that make it attract domestic and foreign tourists not only want to come here to visit but also want to choose this place as a residence. It fully converges the charm of visitors to this place. That city should have so many things to choose from. Because beauty is not only the scenery, beauty also comes from the heart of humanitarian cancer hospitals, with wifi network covering the whole city, with delicious, cheap, impressive food and also with long white sand beaches. poetic not to waste. Next is the climate, the city deserves to live so it has a cool climate, not too hot or too cold. And one more condition for a city to be sustainable, it must be free from theft, social evils. Above are my opinions on the conditions for a city to be sustainable and liveable living, I hope everyone can find a city worth living like that to live happily their whole life.
Chọn C