Bài 4:
a: \(\dfrac{x}{10}=\dfrac{3}{5}\)
=>\(x=10\cdot\dfrac{3}{5}\)
=>x=6(nhận)
b: \(\dfrac{x}{4}=\dfrac{x+1}{8}\)
=>\(2x=x+1\)
=>x=1(nhận)
c: \(\dfrac{x}{5}=\dfrac{5}{6}+\dfrac{-19}{30}\)
=>\(\dfrac{x}{5}=\dfrac{25}{30}-\dfrac{19}{30}\)
=>\(\dfrac{x}{5}=\dfrac{6}{30}=\dfrac{1}{5}\)
=>x=1
d: \(\dfrac{-5}{6}-x=\dfrac{2}{3}\)
=>\(x=-\dfrac{5}{6}-\dfrac{2}{3}=\dfrac{-5-4}{6}=\dfrac{-9}{6}=-\dfrac{3}{2}\left(loại\right)\)
Bài 3:
\(\dfrac{-1}{2}=\dfrac{-1\cdot18}{2\cdot18}=\dfrac{-18}{36}\)
\(\dfrac{5}{12}=\dfrac{5\cdot3}{12\cdot3}=\dfrac{15}{36};\dfrac{7}{18}=\dfrac{7\cdot2}{18\cdot2}=\dfrac{14}{36}\)
\(\dfrac{-5}{9}=\dfrac{-5\cdot4}{9\cdot4}=\dfrac{-20}{36};\dfrac{-1}{3}=\dfrac{-1\cdot12}{3\cdot12}=\dfrac{-12}{36};\dfrac{1}{3}=\dfrac{1\cdot12}{3\cdot12}=\dfrac{12}{36}\)
mà -20<-18<-12<12<14<15
nên \(-\dfrac{5}{9}< -\dfrac{1}{2}< -\dfrac{1}{3}< \dfrac{1}{3}< \dfrac{7}{18}< \dfrac{5}{12}\)
