a: \(\Leftrightarrow\dfrac{2x-2x+8}{x-4}< =0\)
=>8/x-4<=0
=>x-4<=0
hay x<=4
b: \(\Leftrightarrow\dfrac{x-2-x-2}{\left(x-2\right)\left(x+2\right)}< 0\)
\(\Leftrightarrow\left(x-2\right)\left(x+2\right)>0\)
=>x>2 hoặc x<-2
c: \(\Leftrightarrow\dfrac{2x+1-x-1}{x+1}< =0\)
\(\Leftrightarrow\dfrac{x}{x+1}< =0\)
=>-1<x<=0


