`a) x^2 - 2x - 3 ne 0`
`<=>` \(\left[ \begin{array}{l}x \ne 3\\x \ne -1\end{array} \right.\)
`=> D = RR \\ {-1; 3}`
`b)`
\(\left[ \begin{array}{l}x ≥ -\dfrac{5}{3}\\x < -5\end{array} \right.\)
`=> D = (-∞; -5) ∪ [-5/3; +∞)`
`c)`
\(\left[ \begin{array}{l}3 - 2x ≥ 0\\x + 1 > 0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x ≤ \dfrac{3}{2}\\x > -1\end{array} \right.\)
`=> D = (-1; 3/2]`
