Câu 1: D

Câu 3: 53/144>9/170>9/230

\(\dfrac{-9}{7}+\dfrac{5}{-7}< x\le\dfrac{-5}{2}+\dfrac{18}{4}\)

\(\dfrac{-9}{7}+\dfrac{-5}{7}< x\le\dfrac{10}{4}+\dfrac{18}{4}\)

\(\dfrac{-14}{7}< x\le2\)

\(-2< x\le2\)

\(\Rightarrow\)\(x=\left\{-1;0;1;2\right\}\)

-2<-1,0,1,2<2

Bài 1: 

b) ĐKXĐ: \(x\ne3\)

Ta có: \(\dfrac{3-x}{20}=\dfrac{-5}{x-3}\)

\(\Leftrightarrow\dfrac{x-3}{-20}=\dfrac{-5}{x-3}\)

\(\Leftrightarrow\left(x-3\right)^2=100\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=10\\x-3=-10\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=13\left(nhận\right)\\x=-7\left(nhận\right)\end{matrix}\right.\)

Vậy: \(x\in\left\{13;-7\right\}\)

Bài 1 : 

\(=\dfrac{2}{11}+\dfrac{4}{11}-\dfrac{6}{11}-\dfrac{3}{8}-\dfrac{5}{8}=0-1=-1\)

Bài 2 : 

\(\Rightarrow3+x=8\Leftrightarrow x=5\)

Bài 3 : 

\(\Leftrightarrow x-\dfrac{5}{11}=\dfrac{5}{4}\Leftrightarrow x=\dfrac{35}{44}\)

Bài 4 : 

Trong 2 ngày An đọc được số quyên phần quyên sách 

\(\dfrac{1}{11}+\dfrac{8}{11}=\dfrac{9}{11}\)( quyển sách ) 

đs : 9/11 quyển sách 

\(\Leftrightarrow-\dfrac{3}{4}< =x< =\dfrac{1}{2}\)

hay x=0

-12

-3/5 = x/20
-12/20 = x/20
x/20 = -12/20
x/20 = -12 . 20
x/20 = -240
x      = -240 : 20
x      = -12
Vậy số nguyên x dể thỏa mãn đề bài là -12.

-12

\(\dfrac{x}{8}-\dfrac{1}{4}=\dfrac{1}{y}\)

\(\Leftrightarrow\dfrac{x-2}{8}=\dfrac{1}{y}\)

\(\Leftrightarrow x-2=\dfrac{8}{y}\)

Do \(x-2\in Z\Rightarrow\dfrac{8}{y}\in Z\)

\(\Rightarrow y=Ư\left(8\right)\)

\(\Rightarrow y=\left\{-8;-4;-2;-1;1;2;4;8\right\}\)

\(\Rightarrow x=\left\{1;0;-2;-6;10;6;4;3\right\}\)

a, \(\dfrac{4\left(x-3\right)^2-\left(2x-1\right)^2-12x}{12}< 0\)

\(\Rightarrow4\left(x^2-6x+9\right)-4x^2+4x-1-12x< 0\)

\(\Leftrightarrow-32x+35< 0\Leftrightarrow x>\dfrac{35}{32}\)

b, \(\dfrac{24+12\left(x+1\right)-36+3\left(x-1\right)}{12}< 0\)

\(\Rightarrow-12x+15x+9< 0\Leftrightarrow3x< -9\Leftrightarrow x>-3\)