Bài 2:
a: \(\dfrac{x}{5}=\dfrac{3}{15}\)
=>\(\dfrac{x}{5}=\dfrac{1}{5}\)
=>x=1
b: \(\dfrac{x+1}{-3}=\dfrac{-27}{x+1}\)
=>\(\left(x+1\right)^2=\left(-3\right)\cdot\left(-27\right)=81\)
=>\(\left[{}\begin{matrix}x+1=9\\x+1=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-10\end{matrix}\right.\)
Bài 3:
a: -9<-6
=>\(\dfrac{-9}{23}< -\dfrac{6}{23}\)
=>\(\dfrac{-9}{23}< \dfrac{6}{-23}\)
b: \(\dfrac{-5}{12}=\dfrac{-5\cdot5}{12\cdot5}=\dfrac{-25}{60}\)
\(\dfrac{7}{-30}=\dfrac{-7}{30}=\dfrac{-7\cdot2}{30\cdot2}=\dfrac{-14}{60}\)
mà -25<-14
nên \(\dfrac{-5}{12}< \dfrac{7}{-30}\)
c: \(\dfrac{-500}{1400}=\dfrac{-5}{14}=\dfrac{-5\cdot6}{14\cdot6}=\dfrac{-30}{84}\)
mà -30>-9
nên \(-\dfrac{30}{84}>-\dfrac{9}{84}\)
=>\(\dfrac{-500}{1400}>-\dfrac{9}{84}\)
Bài 5:
