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a)\(\frac{1}{8}>0;\frac{-3}{7}< 0\Rightarrow\frac{1}{8}>0>\frac{-3}{7}\Rightarrow\frac{1}{8}>\frac{-3}{7}\)
b)\(\frac{-3}{7}< 0;2\frac{1}{2}>0\Rightarrow\frac{-3}{7}< 0< 2\frac{1}{2}\Rightarrow\frac{-3}{7}< 2\frac{1}{2}\)
c)\(-3,9< 0;0,1>0\Rightarrow-3,9< 0< 0,1\Rightarrow-3,9< 0,1\)
d)\(-2,3< 0;3,2>0\Rightarrow-2,3< 0< 3,2\Rightarrow-2,3< 3,2\)
\(\dfrac{2}{15}=\dfrac{4}{30}>\dfrac{3}{20}\)
\(\Rightarrow\dfrac{-2}{15}=\dfrac{-4}{30}< \dfrac{3}{-20}\)
\(-\dfrac{2}{15}=-\dfrac{8}{60}\)
\(\dfrac{3}{-20}=-\dfrac{3}{20}=-\dfrac{9}{60}< -\dfrac{8}{60}\)
\(\Rightarrow\dfrac{3}{-20}< -\dfrac{2}{15}\)
a) Ta có: \(\dfrac{34}{35}< 1;\dfrac{21}{20}>1\Rightarrow\dfrac{34}{35}< 1< \dfrac{21}{20}\)
Vậy \(\dfrac{34}{35}< \dfrac{21}{20}\)
a: \(\dfrac{34}{35}< 1< \dfrac{21}{20}\)
b: \(-\dfrac{123}{124}>-1>\dfrac{-321}{312}\)
c: \(\dfrac{1}{31}>\dfrac{1}{41}\)
\(\Leftrightarrow\dfrac{10}{31}+1>\dfrac{10}{41}+1\)
\(\Leftrightarrow\dfrac{41}{31}>\dfrac{51}{41}\)
\(\frac{2\frac{1}{2}x-1}{\frac{2}{3}}=\frac{\frac{-2}{3}}{1-2\frac{1}{2}x}\) ĐKXĐ \(x\ne\frac{2}{5}\)
\(\Leftrightarrow\)\(\frac{\frac{5}{2}x-1}{\frac{2}{3}}=\frac{\frac{2}{3}}{\frac{5}{2}x-1}\)\(\Leftrightarrow\)\(\left(\frac{5}{2}x-1\right)^2=\frac{4}{9}\)\(\Leftrightarrow\)\(\frac{25}{4}x^2-5x+1=\frac{4}{9}\)
\(\Leftrightarrow\)\(\frac{25}{4}x^2-5x+\frac{5}{9}=0\)\(\Leftrightarrow\)\(\frac{25}{4}x^2-\frac{25}{6}x-\frac{5}{6}x+\frac{5}{9}=0\)
\(\Leftrightarrow\)\(\left(\frac{25}{4}x^2-\frac{25}{6}x\right)-\left(\frac{5}{6}x-\frac{5}{9}\right)=0\)\(\Leftrightarrow\)\(\frac{25}{2}x\left(\frac{1}{2}x-\frac{1}{3}\right)-\frac{5}{3}\left(\frac{1}{2}x-\frac{1}{3}\right)=0\)
\(\Leftrightarrow\)\(\left(\frac{25}{2}x-\frac{5}{3}\right)\left(\frac{1}{2}x-\frac{1}{3}\right)=0\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=\frac{2}{3}\\x=\frac{2}{15}\end{cases}}\)
Lời giải:
a. $\frac{3}{-7}=\frac{-27}{63}$
$\frac{-5}{9}=\frac{-35}{63}$
Do $\frac{27}{63}< \frac{35}{63}$ nên $\frac{-27}{63}> \frac{-35}{63}$
$\Rightarrow \frac{3}{-7}> \frac{-5}{9}$
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b.
$-0,625=\frac{-625}{1000}=\frac{-5}{8}=\frac{-125}{200}$
$\frac{-19}{50}=\frac{-76}{200}> \frac{-125}{200}$
$\Rightarrow -0,625> \frac{-19}{50}$
c.
$-2\frac{5}{9}=-(2+\frac{5}{9})=\frac{-23}{9}=-(\frac{-23}{-9})$
ôi trời :-3.9<0 và 0.1>0 =>-3.9>0.1
-2.3<0 và 3.2>0 =>-2.3<3.2
bạn ơi giúp mình làm thành phân số được hông