Bài 1:

\(A=\dfrac{3-2x}{x-1}>0\)

\(TH_1:\left\{\begin{matrix}3-2x>0\\ x-1>0\end{matrix}\right. \Leftrightarrow \left\{\begin{matrix}x<\dfrac{3}{2}\\ x>1\end{matrix}\right. \Leftrightarrow 1< x<\dfrac{3}{2}\)

\(TH_2:\left\{\begin{matrix}3-2x<0\\ x-1<0\end{matrix}\right.\Leftrightarrow \left\{\begin{matrix}x>\dfrac{3}{2}\\ x<1\end{matrix}\right.\) (loại)

\(A>0\Leftrightarrow1< x< \dfrac{3}{2}\)

Bài 2:

\(x-xy+y-2=3\\ \Leftrightarrow-x\left(y-1\right)+\left(y-1\right)=4\\ \Leftrightarrow\left(y-1\right)\left(x-1\right)=-4\)

Vì \(x,y\in Z\Rightarrow x-1\) và \(y-1\inƯ\left(-4\right)=\left\{\pm1;\pm2;\pm4\right\}\)

Ta có bảng sau:

Vậy...

Bài 3:

\(B=\dfrac{2x^2-3}{x-1}=\dfrac{2x^2-2-1}{x-1}=\dfrac{2\left(x+1\right)\left(x-1\right)-1}{x-1}=2\left(x+1\right)-\dfrac{1}{x-1}\)

Để B nguyên \(\Leftrightarrow\dfrac{1}{x-1}\) nguyên \(\Rightarrow1⋮x-1\Rightarrow x-1\inƯ\left(1\right)=\left\{-1;1\right\}\\ \Rightarrow x\in\left\{0;2\right\}\)

Mà \(x\in N\Rightarrow x=2\)

Vậy...

Jane really love the ______ jewelry box that her parents gave her as a birthday present

A. nice wooden brown.

B. brown wooden nice.

C. nice brown wooden.

D. wooden brown nice

Mark the letter A, B, C or D on your answer sheet to indicate the word that differs from the other three in the position of primary stress in each of the following questions.

A. attitide   

B. partnership       

C. romantic 

D. actually

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35.

DO SMALLER CLASSES REALLY HELP?

 In an experiment in Canada, ten-year-old children were put in classes of four sizes: 16, 23, 30 and 37 children in (31)____ class. Their teachers said that the smaller classes would result in more individual attention and better marks. However, when the children were (32)____, those in the smaller classes didn’t get higher marks than the others, except in mathematics. Moreover, children in the larger classes said they liked school (33)____ as much. Perhaps the most surprising result was the difference between what teachers expected and the actual results obtained. More than 90% of the teachers expected the smaller classes to (34)____ well. After teaching these smaller classes, over 80% of the teachers thought the pupils had done better. However, according to the researchers, nothing of the (35)____ happened. Class size seemed to make a difference only to the teachers’ own attitudes - and not to the results they obtained. (Source: “Longman Tests in Contexts” by J.B. Heaton)

Điền ô số 31

A. every 

B. one 

C. each 

D. either 

Read the passage and choose the best answer.

A pilot cannot fly by sight alone. In many conditions, such as flying at night and landing in dense fog, a pilot must use radar, an alternative way of navigating. Since human eyes are not very good at determining speeds of approaching objects, radar can show a pilot how fast nearby planes are moving. The basic principle of radar is exemplified by what happens when one shouts in a cave. The echo of the sounds against the walls helps a person determine the size of the cave. With radar, however, the waves are radio waves instead of sound waves. Radio waves travel at the speed of light, about 300,000 kilometers in one second. A radar set sends out a short burst of radio waves. Then it receives the echoes produced when the waves bounce off objects. By determining the time it takes for the echoes to return to the radar set, a trained technician can determine the distance between the radar set and other objects. The word “radar”, in fact, gets its name from the term “radio detection and ranging”. “Ranging” is the term for detection of the distance between an object and the radar set. Besides being of critical importance to pilots, radar is essential for air traffic control, tracking ships at sea, and for tracking weather systems and storms. 

Which of the following words best describes the tone of this passage?  

A. argumentative

B. explanatory 

C. humorous 

D. imaginative

Ta có: \(n_{KMnO_4}=\dfrac{5,53}{158}=0,035\left(mol\right)\)

\(PTHH:2KMnO_4\xrightarrow[]{t^o}K_2MnO_4+MnO_2+O_2\uparrow\left(1\right)\)

Theo PTHH (1):

\(n_{O_2}=\dfrac{1}{2}n_{KMnO_4}=\dfrac{1}{2}.0,035=0,0175\left(mol\right)\)

Số mol oxi tham gia phản ứng là: \(n_{O_2pư}=80\%.0,0175=0,014\left(mol\right)\)

Gọi n là hóa trị của R, n có thể nhận các giá trị 1, 2, 3 (*)

=> PTPƯ đốt cháy.

\(4R+nO_2\xrightarrow[]{t^o}2R_2O_n\left(2\right)\)

Theo PTHH (2)

\(n_R=\dfrac{4}{n}.n_{O_2}=\dfrac{4}{n}.0,014=\dfrac{0,056}{n}\left(mol\right)\)

Mà khối lượng của R đem đốt là: \(m_R=0,672gam\)

\(\Rightarrow M_R=\dfrac{m_R}{n_R}=\dfrac{0,672}{\dfrac{0,056}{n}}=12n\) (**)

Từ (*) và (**) ta có bảng sau:

Vậy R là kim loại có hóa trị II và cso nguyên tử khối là 24

=> R là Magie: Mg

Gọi số đó là ab số viết theo thứ tự ngược lại là ba

Ta có:

ab+ba=10.a+b + 10.b+a

=11.a +11.b =11.(a+b) chia hết cho 11

=>Tổng của 1 số có 2 chữ số và số đó viết theo thứ tự ngược lại chia hết cho 11