Đáp án:
2.a)S={${x/\frac{-3}{2}<x<1}$}
b)S={${x/x>\frac{3}{4};x<-5}$}
3. S={${x/x\geq\frac{7}{2}}$}
Giải thích các bước giải:
${2.\\ a)(2x+3).(x-1)<0\\ \Rightarrow \left[ \begin{array}{l}2x+3<0;x-1>0\\2x+3>0;x-1<0\end{array} \right. \\ \Leftrightarrow \left[ \begin{array}{l}x<\frac{-3}{2};x>1\\x>\frac{-3}{2};x<1\end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l}1<x<\frac{-3}{2}(vô-lý)\\\frac{-3}{2}<x<1(thỏa-mãn)\end{array} \right.\\}$
Vậy S={${x/\frac{-3}{2}<x<1}$}
${b)(x+5).(4x-3)>0\\ \Leftrightarrow \left[ \begin{array}{l}x>-5;x>\frac{3}{4}\\x<-5;x<\frac{3}{4}\end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l}x>\frac{3}{4}\\x<-5\end{array} \right.\\}$
Vậy S={${x/x>\frac{3}{4};x<-5}$}
${3.\\\frac{-7}{2}+x\geq0\\ \Leftrightarrow x\geq\frac{7}{2}}$
Vậy S={${x/x\geq\frac{7}{2}}$}
