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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) \(-\frac{5}{6}+\frac{8}{3}+-\frac{29}{6}\le x\le-\frac{1}{2}+2+\frac{5}{2}\)
\(\Rightarrow-3\le x\le4\)
\(\Rightarrow x\in\left\{-3;-2;-1;0;1;2;3;4\right\}\)
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Do \(a,b,c\in Z^+\)=> \(\frac{a}{a+b}>\frac{a}{a+b+c}\)\(\frac{b}{b+c}>\frac{b}{a+b+c}\)và \(\frac{c}{c+a}>\frac{c}{a+b+c}\)
\(\Rightarrow\frac{a}{a+b}+\frac{b}{b+c}+\frac{c}{c+a}>\frac{a}{a+b+c}+\frac{b}{a+b+c}+\frac{c}{a+b+c}=1\)
Giả sử \(a\ge b\ge c\)Ta có \(a,b,c\in Z^+\)và \(a\ge b\)\(\Rightarrow\)\(c+a\ge c+b\)\(\Rightarrow\frac{c}{c+a}\le\frac{c}{c+b}\Rightarrow\frac{b}{b+c}+\frac{c}{c+a}\le\frac{b}{b+c}+\frac{c}{c+b}=1\)
Do \(a,b,c\in Z^+\)\(\Rightarrow\frac{a}{a+b}< 1\Rightarrow\frac{a}{a+b}+\frac{b}{b+c}+\frac{c}{c+a}< 2\)
Vậy \(\frac{a}{a+b}+\frac{c}{b+c}+\frac{a}{c+a}\le2\)
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a ) \(\frac{x}{3}-\frac{10}{21}=-\frac{1}{7}\)
\(\frac{x}{3}=-\frac{1}{7}+\frac{10}{21}\)
\(\frac{x}{3}=-\frac{3}{21}+\frac{10}{21}\)
\(\frac{x}{3}=-\frac{13}{21}\)
\(x:3=-\frac{13}{21}\)
\(x=-\frac{13}{21}.3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Đề bài thiếu : \(x\inℤ\)
Ta có :
\(\frac{-5}{6}+\frac{8}{3}+\frac{-29}{6}\le x\le\frac{-1}{2}+2+\frac{5}{2}\)
\(\Leftrightarrow\)\(\frac{-5+16-29}{6}\le x\le\frac{-1+4+5}{2}\)
\(\Leftrightarrow\)\(\frac{-18}{6}\le x\le\frac{8}{2}\)
\(\Leftrightarrow\)\(-3\le x\le4\)
\(\Rightarrow\)\(x\in\left\{-3;-2;-1;0;1;2;3;4\right\}\)
Vậy \(x\in\left\{-3;-2;-1;0;1;2;3;4\right\}\)
Chúc bạn học tốt ~
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\(\Leftrightarrow\frac{-2}{17}\le\frac{x}{17}\le\frac{2}{17}\Rightarrow x\in\left(-2;-1;0;1;2\right)\)
\(\Leftrightarrow\frac{-1}{24}\le\frac{x}{24}\le\frac{5}{24}\Rightarrow x\in\left(-1;0;1;2;3;4;5\right)\)
2 câu sau tự làm nha
\(-\frac{5}{17}+\frac{3}{17}\le\frac{x}{17}\le\frac{13}{17}+-\frac{11}{17}\)
\(\frac{-2}{17}\le\frac{x}{17}\le\frac{2}{17}\)
=> \(x\in\left\{-2;-1;0;1;2\right\}\)
\(25\%+\frac{2}{5}\le x\%\le1-0,3\)
\(\Rightarrow\frac{13}{20}\le\frac{x}{100}\le\frac{7}{10}\)
\(\Rightarrow\frac{13}{20}.100\le x\le\frac{7}{10}.100\)
\(\Rightarrow65\le x\le70\)
\(\Rightarrow x\in\left\{65;66;67;68;69;70\right\}\)