a) \(2x-3>5x+10\) \(\Leftrightarrow\) \(2x-5x>10 +3\Leftrightarrow-3x>13\Leftrightarrow x< \dfrac{13}{-3}\) vậy \(x< \dfrac{13}{-3}\)
b) \(2x^2-3x>x+7x\) \(\Leftrightarrow\) \(2x^2-3x-x-7x>0\)
\(\Leftrightarrow\) \(2x^2-11x>0\) \(\Leftrightarrow\) \(x\left(2x-11\right)>0\) \(\Leftrightarrow\) \(\left\{{}\begin{matrix}x>0\\2x-11>0\end{matrix}\right.\)\(\Leftrightarrow\) \(\left\{{}\begin{matrix}x>0\\x>\dfrac{11}{2}\end{matrix}\right.\)
\(\Rightarrow\) \(x>\dfrac{11}{2}\) vậy \(x>\dfrac{11}{2}\)
c) \(\left(x-1\right)\left(x+3\right)< 0\) \(\Leftrightarrow\) \(x^2+3x-x-3< 0\)
\(\Leftrightarrow\) \(x^2+2x-3>0\) \(\Leftrightarrow\) \(x^2-x+3x-3>0\)
\(\Leftrightarrow\) \(x\left(x-1\right)+3\left(x-1\right)\) \(\Leftrightarrow\) \(\left(x+3\right)\left(x-1\right)\)
\(\Leftrightarrow\) \(\left\{{}\begin{matrix}x-1>0\\x+3>0\end{matrix}\right.\)\(\Leftrightarrow\) \(\left\{{}\begin{matrix}x>1\\x>-3\end{matrix}\right.\) \(\Rightarrow\) \(x>1\) vậy \(x>1\)
