[tex]f(x) = \frac{2}{ {x}^{2} + 4x} \\ {x}^{2} + 4x\neq0 \\ x(x + 4)\neq0 \\ x_{1}\neq0 \\ x_{2}\neq - 4 \\ x \: \epsilon \: ( - \propto; \: - 4)U( - 4; \: 0)U(0; \: + \propto)[/tex]