a) (x+2)(x-3) <0 \(\Leftrightarrow\)x+2>0 , x-3 <0 hoặc x+2<0 , x-3 >0 ( loại)
\(\Leftrightarrow\)-2<x<3
b) \(\left(x-1\right)\left(x-2\right)\ge0\)
\(\Leftrightarrow\)x-1\(\ge\)0 , x-2 \(\ge\)0 hoặc x-1 \(\le0\), x-2 \(\le0\)
\(\Leftrightarrow\)\(1\le x\)hoặc \(x\ge2\)
c) ta có \(x^2+1>0\)\(\Rightarrow\)x+2 >0 \(\Leftrightarrow\)x>-2