[tex] {x}^{2} + 2x + 4 = 0 \\ \Leftrightarrow {x}^{2} + 2x + 1 = - 4 + 1 \\ \Leftrightarrow \underbrace{ {(x + 1)}^{2} }_{ \geqslant 0} = - 3 \\ \Leftrightarrow x\in\emptyset[/tex]
