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28 tháng 7 2016
a)\(\frac{-5}{6}\).\(\frac{120}{25}\)<x<\(\frac{-7}{15}\).\(\frac{9}{14}\)
-4 <x<\(\frac{-3}{10}\)
\(\frac{-40}{10}\)< x <\(\frac{-3}{10}\)=>x E {-39:-38:-37:.....:-4}
b)\(\left(\frac{-5}{3}\right)^3\)<x<\(\frac{-24}{35}.\frac{-5}{6}\)
\(\frac{-875}{189}< x< \frac{108}{189}\)
=> x E {\(\frac{-874}{189},\frac{-873}{189},......,\frac{107}{189}\)}
AT
19 tháng 2 2017
a/ \(\frac{2}{3}+\frac{4}{35}< \frac{x}{105}< \frac{1}{7}+\frac{2}{5}+\frac{1}{3}\)
\(\Rightarrow\frac{82}{105}< \frac{x}{105}< \frac{92}{105}\)
\(\Rightarrow82< x< 92\)
\(\Rightarrow x=\left\{83;84;85;86;87;88;89;90;91\right\}\)
b/ \(-\frac{7}{15}+\frac{8}{60}+\frac{24}{90}\le\frac{x}{15}\le\frac{3}{5}+\frac{8}{30}+-\frac{4}{10}\)
\(\Rightarrow-\frac{1}{15}\le\frac{x}{15}\le\frac{7}{15}\)
\(\Rightarrow-1\le x\le7\)
\(\Rightarrow x=\left\{-1;0;1;2;3;4;5;6;7\right\}\)
KN
25 tháng 3 2019
1) \(\frac{-5}{6}.\frac{120}{25}< x< \frac{-7}{15}.\frac{9}{14}\)
\(\Leftrightarrow\frac{-5}{6}.\frac{24}{5}< x< \frac{-63}{210}\)
\(\Leftrightarrow-40< x< \frac{-63}{210}\)
\(\Leftrightarrow\frac{-400}{10}< \frac{10x}{10}< \frac{-3}{10}\)
\(\Leftrightarrow-400< 10x< -3\)
\(\Leftrightarrow x\in\left\{-39;-38;...;-2;-1\right\}\)
2) \(\left(\frac{-5}{3}\right)^3< x< \frac{-24}{35}.\frac{-5}{6}\)
\(\Leftrightarrow\frac{-125}{25}< x< \frac{4}{7}\)
\(\Leftrightarrow\frac{-35}{7}< \frac{-7x}{7}< \frac{4}{7}\)
\(\Leftrightarrow-35< -7x< 4\)
\(\Leftrightarrow x\in\left\{4;3;2;1;0\right\}\)
B
2 tháng 4 2019
1)
a)
\(\frac{-5}{6}.\frac{120}{25}< x< \frac{-7}{15}.\frac{9}{14}\)
\(\frac{-1}{1}.\frac{20}{5}< x< \frac{-1}{5}.\frac{3}{2}\)
\(\frac{-20}{5}< x< \frac{-3}{10}\)
\(\frac{-40}{10}< x< \frac{-3}{10}\)
\(\Rightarrow Z\in\left\{-4;-5;-6;-7;-8;-9;-10;...;-39\right\}\)
29 tháng 1 2019
\(\frac{3}{x-5}=-\frac{4}{x+2}\)
\(\Leftrightarrow3\left(x+2\right)=-4\left(x-5\right)\)
\(\Leftrightarrow3x+6=-4x+20\)
\(\Leftrightarrow7x=14\)
\(\Leftrightarrow x=2\)
\(\frac{x}{-2}=-\frac{8}{x}\)
\(\Leftrightarrow x^2=16\)
\(\Leftrightarrow x=\pm4\)
\(-\frac{2}{x}=\frac{y}{3}\)
\(\Leftrightarrow xy=-6\)
\(\Leftrightarrow x;y\inƯ\left(-6\right)=\left\{\pm1;\pm2;\pm3;\pm6\right\}\)
Xét bảng
| x | 1 | -1 | 2 | -2 | 3 | -3 | 6 | -1 |
| y | -6 | 6 | -3 | 3 | -2 | 2 | -1 | 6 |
Vậy.................
\(\frac{2x-9}{240}=\frac{39}{80}\)
\(\Leftrightarrow2x-9=\frac{240.39}{80}\)
\(\Leftrightarrow2x-9=117\)
\(\Leftrightarrow2x=126\)
\(\Leftrightarrow x=63\)
NH
0
20 tháng 2 2017
a) \(-\frac{2x}{5}=\frac{-6}{3}\)
\(\Rightarrow-2x.3=-6.5\)
\(\Rightarrow-2x=\frac{-6.5}{3}\)
\(\Rightarrow-2x=-10\)
\(\Rightarrow x=\frac{-10}{-2}\)
\(\Rightarrow x=5\)
b) \(\frac{x-2}{18}=\frac{-1}{6}\)
\(\Rightarrow\left(x-2\right).6=-1.18\)
\(\Rightarrow x-2=\frac{-1.18}{6}\)
\(\Rightarrow x-2=-3\)
\(\Rightarrow x=-3+2\)
\(\Rightarrow x=-1\)
c) \(\frac{x}{14}=\frac{6}{y}=\frac{-15}{35}\)
\(\Rightarrow\left[\begin{matrix}\frac{x}{14}=\frac{-15}{35}\\\frac{6}{y}=\frac{-15}{35}\end{matrix}\right.\Rightarrow\left[\begin{matrix}x.35=-15.14\\6.35=-15.y\end{matrix}\right.\)
\(\Rightarrow\left[\begin{matrix}x=\frac{-15.14}{35}\\y=\frac{6.35}{-15}\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-6\\y=-14\end{matrix}\right.\)
Vậy \(x=-6;y=-14\)
HN
20 tháng 2 2017
a) \(\frac{-2x}{5}=-\frac{6}{3}\)
\(\Leftrightarrow-6x=-30\)
\(\Leftrightarrow x=5\)
b) \(\frac{x-2}{18}=-\frac{1}{6}\)
\(\Leftrightarrow-6\left(x-2\right)=-18\)
\(\Leftrightarrow x-2=3\)
\(\Leftrightarrow x=5\)
c) \(\frac{x}{14}=\frac{6}{y}=-\frac{15}{35}\)
\(\Leftrightarrow\frac{x}{14}=\frac{6}{y}=-\frac{3}{7}\)
\(\Leftrightarrow\left\{\begin{matrix}x=-6\\y=-14\end{matrix}\right.\)
\(\frac{-24}{35}.\frac{6}{15}< x< 4\)
=>Vi (-24).6<35.15=>-1<x<4
=>x\(\in\){0,1,2,3}