`a) 2x + 1 ne 0`
`-> x ne -1/2`
`b)` \(\left\{ \begin{array}{l}x + 3≥0\\2x + 1 \ne 0\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}x ≥ -3\\x \ne \dfrac{-1}{2}\end{array} \right.\)
`c) 3 - x >0 -> x < 3`
`d)` \(\left\{ \begin{array}{l}2x + 1 \ne 0\\x - 2 > 0\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}x \ne \dfrac{-1}{2}\\x > 2\end{array} \right.\)
`-> x > 2`
`e) 25 - x^2 > 0`
`-> -5 < x < 5`
`f) x^2 - 9 >= 0`
`->` \(\left[ \begin{array}{l}x < -3\\x > 3\end{array} \right.\)
