= 14,226315013997347870929718579638

\(\dfrac{-12n}{n}=-12\)

=> Với mọi n thì \(\dfrac{-12n}{n}\) đều có giá trị nguyên.(1)

Đề \(\dfrac{15}{n-2}\) nguyên <=> \(n-2\inƯ\left(15\right)=\left\{\pm1;\pm3;\pm5;\pm15\right\}\\ \Rightarrow n\in\left\{-13;\pm3;\pm1;5;7;17\right\}\left(2\right)\)

Để \(\dfrac{8}{n+1}\) nguyên <=> \(n+1\inƯ\left(8\right)=\left\{\pm1;\pm2;\pm4;\pm8\right\}\\ \Rightarrow n\in\left\{-9;-5;\pm3;-2;0;1;7\right\}\left(3\right)\)

Từ (1), (2) và (3) => Để \(\dfrac{-12n}{n};\dfrac{15}{n-2};\dfrac{8}{n+1}\) đồng thời có giá trị nguyên thì \(n\in\left\{\pm3;1;7\right\}\). Mà \(n\in N\Rightarrow n\in\left\{1;3;7\right\}\)

Gọi độ dài quãng đường AB là \(x(km)(x>0)\)

=> Vận tốc của ô tô thứ nhất là: \(\dfrac{x}{5}(km/h)\)

Vận tốc của ô tô thứ hai là: \(\dfrac{x}{6}(km/h)\)

Khi đó sau 2 giờ ô tô thứ nhất đi được: \(\dfrac{2x}{5}\left(km\right)\)

_____________________hai đi được: \(\dfrac{2x}{6}\left(km\right)\)

Vì sau 2 giờ hai ô tô còn cách nhau 80km nên ta có pt:

\(\dfrac{2x}{5}+\dfrac{2x}{6}+80=x\\\Leftrightarrow \dfrac{12x+10x-30x}{30}=\dfrac{-2400}{30}\\ \Rightarrow-8x=-2400\\\Leftrightarrow x=300\left(TM\right)\)

Vậy độ dài quãng đường AB là 300km

hiệu giữa tử và mẫu băng: 91-52= 39

coi tử số lúc sau là 1 phần, mẫu số lúc sau là 2 phần

Hiệu số phần tử số và mẫu số lúc sau: 2- 1 = 1

tử số lúc sau: (39 :1)x1 =39

phải bớt đi: 52 – 39 = 13 

Read the following passage and mark the latter A, B, C or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks . Fill in the appropriate word in question 36

      Why is it that many teenagers have the energy to play computer games until late at night but can’t find the energy to get out of bed (35) ________ for school? According to a new report, today’s generation of children are in danger of getting so (36)_______ sleep that they are putting their mental and physical health at (37)_______. Adults can easily survive on seven to eight hours’ sleep a  night, (38)_______teenagers require nine or ten hours. According to medical experts, one in five youngsters (39)________ anything between two and five hours’ sleep a night less than their parents did at their age.

      This (40) _____ serious questions about whether lack of sleep is affecting children’s ability to concentrate at school. The connection between sleep deprivation and lapses in memory, impaired reaction time and poor concentration is well (41) _______. Research has shown that losing as little as half an hour’s sleep a night can have profound effects (42) ______how children perform the next day. A good night’s sleep is also crucial for teenagers because it is while they are asleep (43)______ they release a hormone that is essential for their ‘growth spurt’ (the period during teenage years when the body grows at a rapid rate). It’s true that they can, to some (44) ______, catch up on sleep  at weekends, but that won’t help them when they are dropping off to sleep in class on a Friday afternoon.

            By Tim Falla and Paul A.Davies, Solutions Advanced. OUP

A. few

B. less

C. much

D. little

Lượng H₂O₂ và KOH tương ứng được sử dụng để oxi hóa hoàn toàn 0,01 mol KCr(OH)₄ thành K₂CrO₄ là

A. 0,015 mol và 0,01 mol

B. 0,030 mol và 0,04 mol

C. 0,015 mol và 0,04 mol

D. 0,030 mol và 0,04 mol

She said she met you once at the Parade last week. _________since?

A. Have you met her 

B. Had you met her

C. Did you meet her 

D. Were you met her

Biết SABC= bao nhiêu \(cm^2\) vậy bạn

PTĐTTNT hay j z bạn