\(\frac{3}{x-5}=-\frac{4}{x+2}\)

\(\Leftrightarrow3\left(x+2\right)=-4\left(x-5\right)\)

\(\Leftrightarrow3x+6=-4x+20\)

\(\Leftrightarrow7x=14\)

\(\Leftrightarrow x=2\)

\(\frac{x}{-2}=-\frac{8}{x}\)

\(\Leftrightarrow x^2=16\)

\(\Leftrightarrow x=\pm4\)

\(-\frac{2}{x}=\frac{y}{3}\)

\(\Leftrightarrow xy=-6\)

\(\Leftrightarrow x;y\inƯ\left(-6\right)=\left\{\pm1;\pm2;\pm3;\pm6\right\}\)

Xét bảng

Vậy.................

\(\frac{2x-9}{240}=\frac{39}{80}\)

\(\Leftrightarrow2x-9=\frac{240.39}{80}\)

\(\Leftrightarrow2x-9=117\)

\(\Leftrightarrow2x=126\)

\(\Leftrightarrow x=63\)

1)

\(\frac{7.8^3-5.2^{10}}{\left(-16\right)^2}\)       

=  \(\frac{7.2^8.2-5.2^8.2^2}{16^2}\)

=  \(\frac{2^8.\left(2.7-5.2^2\right)}{2^8}\)

=   \(\frac{2^8.\left(-6\right)}{2^8}\)

=   \(-6\)

2)

b)\(\frac{-28}{4}\le x\le\frac{-21}{7}\)

\(\Rightarrow-7\le x\le-3\)

\(\Rightarrow x=\left\{-7;-6;-5;-4;-3\right\}\)

2)

a)\(\frac{108}{12}\le x\le\frac{91}{7}\)

\(\Rightarrow9\le x\le13\)

\(\Rightarrow x=\left\{9;10;11;12;13\right\}\)

A, Theo đề ta có 108/12 = 9 ; 91/7 = 13

Vì \(9\le x\le13\) nên \(x\in\left\{9;10;11;12;13\right\}\)

Vậy \(A=\left\{9;10;11;12;13\right\}\)

B, Theo đề ta có -28/4 = -7 ; -21/7 = -3

Vì \(-7\le x\le-3\) nên \(x\in\left\{-7;-6;-5;-4;-3\right\}\)

Vậy E = {-7 ; -6 ; -5 ; -4 ; -3}

a) \(y=\frac{108}{12}\le x\le\frac{91}{7}\Rightarrow9\le x\le13\)=> E = {x\(\in N ; 9\le x\le13\)} => E = {9;10;11;12;13}

b) \(y=\frac{-28}{4}\le x\le\frac{-21}{7}\Rightarrow-7\le x\le-3\)=> Không có số tự nhiên nào thỏa mãn nên E là tập hợp rỗng

\(a.\frac{2}{x}=\frac{x}{8}\)

\(\Rightarrow x^2=2.8\)

\(\Rightarrow x^2=16\)

\(\Rightarrow x^2=4^2\)

\(\Rightarrow x=4\)

\(b.\frac{-28}{4}\le x\le\frac{-21}{7}\)

\(\Rightarrow\frac{-196}{28}\le\frac{28x}{28}\le\frac{-84}{28}\)

\(\Rightarrow-196\le28x\le-84\)

Mà \(28x⋮28\)

\(\Rightarrow28x\in\left\{-84;-112;-140;-168;-196\right\}\)

\(\Rightarrow x\in\left\{-3;-4;-5;-6;-7\right\}\)

a, =>x.x=2.8

=>x²=16=4²=-4²=2⁴=-2⁴

1,x=4 ; 2,x=-4 ; 3,x=2 ; 4,x=-2

b, =>-7 \<x\<-3

=>x=-6;-5;-4

dấu \< thay cho dấu nhỏ hơn hoặc bằng nha bạn !!!!!!!!!
 

8/12=4/6;7/14=21/42

k mình nha

Ai nhanh nhat mk tk

\(\frac{8}{12}=\frac{4}{6};\frac{7}{14}=\frac{21}{42}\)

Tk mk mk tk lại ! ^^ 

a) \(\frac{x}{3}-\frac{10}{21}=-\frac{1}{7}\)

\(\Rightarrow\frac{x}{3}=-\frac{1}{7}+\frac{10}{21}\)

\(\Rightarrow\frac{x}{3}=\frac{7}{21}\)

\(\Rightarrow\frac{x}{3}=\frac{1}{3}\)

\(\Rightarrow x=1\)

\(x-25\%=\frac{1}{2}\)

\(\Rightarrow x-\frac{1}{4}=\frac{1}{2}\)

\(\Rightarrow x=\frac{1}{2}+\frac{1}{4}\)

\(\Rightarrow x=\frac{3}{4}\)

c) \(-\frac{5}{6}+\frac{8}{3}+-\frac{29}{6}\le x\le-\frac{1}{2}+2+\frac{5}{2}\)

\(\Rightarrow-3\le x\le4\)

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

a)x/3-10/21=-1/7

 x/3=-1/7+10/21

x/3=1/3

=> x= 1

b/ x-25%=1/2

      x-1/4=1/2

             x=1/2+1/4

             x=3/4

c) x=-2 nha

d) =\(\frac{1}{5.6}\)+\(\frac{1}{6.7}\)+......+\(\frac{1}{11.12}\)

=\(\frac{1}{5}\)-\(\frac{1}{6}\)+\(\frac{1}{6}\)-\(\frac{1}{7}\)+.....+\(\frac{1}{11}\)-\(\frac{1}{12}\)

=\(\frac{1}{5}\)-\(\frac{1}{12}\)= \(\frac{7}{60}\)

bạn ơi kết quả là 7/60

\(=\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{11.12}\)

\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{12}\)

\(=\frac{1}{5}-\frac{1}{12}\)

\(=\frac{7}{60}\)

\(a)\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}\le x< \frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}\)

\(\Rightarrow\frac{1}{3}+\frac{1}{6}+\frac{-2}{5}+\frac{-1}{5}\le x< \frac{-3}{4}+\frac{-1}{4}+\frac{2}{7}+\frac{5}{7}+\frac{3}{5}\)

\(\Rightarrow\frac{2}{6}+\frac{1}{6}+\frac{-3}{5}\le x< -1+1+\frac{3}{5}\)

\(\Rightarrow\frac{1}{2}+\frac{-3}{5}\le x< \frac{3}{5}\)

\(\Rightarrow\frac{-1}{10}\le x< \frac{6}{10}\)

\(\Rightarrow-1\le x< 6\)

\(\Rightarrow x\in\left\{-1;0;1;2;3;4;5\right\}\)

Bài b tương tự

bạn ơi bạn giải câu b được ko. mk ko biết làm câu b