$|x| ≤ 4$
$x= 0; ±1; ±2; ±3; ±4$
$(-4)+(-3)+...+3+4$
$=(-4+4)+...+(-3+3)$
$=0+..+0$
$=0$
Đáp án:
Có $|x|≥0\quad ∀x$
$→$ Để $|x|≤4→0≤|x|≤4$
$→x∈\{-4;-3;-2;-1;0;1;2;3;4\}$
$→$ Tổng = 0
1 Mark the letter A, B, C or D to indicate the most suitable response to complete each of the following exchanges. “My favorite leisure activity is people watching.” “_______” A: That’s all right. B: OK. That’s very kind of you C: That sounds so weird! D: Sure. It’s very entertaining. Choose the best answer a, b, c or d to complete the sentence. Question 5. How much time do you spend _______ leisure activities? A: on B: for C: with D: in 4 Choose the sentence so that it has similar meaning to the first one. Question 22. She likes to hang out with friends on Saturday evening. A: She’s fancy hanging out with friends on Saturday evening. B: She’s keen in hanging out with friends on Saturday evening. C: She’s interested in hang out with friends on Saturday evening. D: She’s interested in hanging out with friends on Saturday evening. 5 Read the passage carefully, then choose the correct answers. The latest addiction to trap thousands of people is the Internet, which has been blamed for broken relationships, job losses, financial ruin, and even suicide. Psychologists now recognize Internet Addiction Syndrome (IAS) as a new illness that could cause serious problems and ruin many lives. IAS is similar to other problems like gambling, smoking and drinking: addicts have dreams about the Internet; they need to use it as the first thing in the morning; they lie to their parents and partners about how much time they spent online; they wish they could cut down, but are unable to do so. A recent study found that many users spend up to 40 hours a week on the Internet. Some of the addicts are teenagers who are already hooked on computer games and who find it very difficult to resist the games on the Internet. Internet addicts find it hard ___________. A: to use the Internet in the morning B: to spend more time on the Internet C: to lie about the time they spent online D: to spend less time on the Internet 6 Read the passage carefully, then choose the correct answers. The latest addiction to trap thousands of people is the Internet, which has been blamed for broken relationships, job losses, financial ruin, and even suicide. Psychologists now recognize Internet Addiction Syndrome (IAS) as a new illness that could cause serious problems and ruin many lives. IAS is similar to other problems like gambling, smoking and drinking: addicts have dreams about the Internet; they need to use it as the first thing in the morning; they lie to their parents and partners about how much time they spent online; they wish they could cut down, but are unable to do so. A recent study found that many users spend up to 40 hours a week on the Internet. Some of the addicts are teenagers who are already hooked on computer games and who find it very difficult to resist the games on the Internet. The word ‘it’ in paragraph 2 refers to ___________. A: dream B: computer C: the Internet D: IAS 7 Choose the sentence so that it has similar meaning to the first one. Question 25. DIY skills aren’t as hard to learn as I think. A: DIY skills are easier to learn than I think. B: DIY skills are easier to learn. C: DIY skills are easier to learn as I think. D: I think DIY skills are easier to learn. 8 Choose the best answer a, b, c or d to complete the sentence. Question 7. On YouTube you can find many videos on _______ all aspects of your English. A: improving B: working C: surfing D: taking
Giúp mình với Tìm x,y x²-x+y²+y+1/2=0
cho Tam giác ABC cân tại A ( A<90 độ )vẽ BD vuông góc AC CE vuông góc AB Gọi H là giao điểm của BD CE a) cm tam giác ABD = tam giác ACE b)cm tam giác AED cân c) cm AH là đừng trung trực của ED d) trên tia đối tia DB lấy điểm K sao cho DK=DB cm góc ECB= góc DKC
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để điều chế đc 48 gam khí oxi thì cần bao nhiêu mol kali corat (KCLO3) để phân hủy
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Dẫn hỗn hợp gồm 0,01 mol CH4;0,02 mol C2H4 và 0,03 mol C2H2 lần lượt đi qua bình (1) chứa lượng dư dung dịch AgNo3 trong NH3;bình (2) chứa dung dịch Br2 (dư),thấy khối lượng dung dịch trong bình (1) giảm a gam và khối lượng Br2 trong bình (2) đã phảnưng là b gam.Tổng giá trị a+b là bao nhiêu?
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Làm hộ mình bài 5 với mình đang cần gấp
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