3.
[tex]f(x) = \frac{6}{x^{2}+8x+7}\\\\M. \ zerowe\\\\x^{2}+8x+7 =0\\\\x^{2}+x+7x+7 = 0\\\\x(x+1)+7(x+1) = 0\\\\(x+1)(x+7) = 0\\\\x+1 = 0 \ \vee \ x+7 = 0\\\\x = -1 \ \vee \x = -7\\\\D = R \setminus\{-7,-1\}\\\\\\\boxed{Odp. \ C. \ g(x) = \frac{1}{x+1} -\frac{1}{x+7}} \ \ D = R\setminus\{-7,-1\}[/tex]
4.
[tex]f(x) = \frac{x-1}{x} + \frac{x}{x+3} + \frac{2x-2}{x-\sqrt{2}} + \frac{x-2}{x^{2}+2}\\\\x \neq 0 \\ i\\x+3 \neq 0 \ \ \rightarrow \ \ x \neq -3\\i\\x-\sqrt{2}\neq 0 \ \ x \neq \sqrt{2}\\\\x^{2}+2 > 0, \ dla \ kazdego \ x\\\\\boxed{D = R\setminus\{-3,0,\sqrt{2}\}}\\\\\underline{Odp. \ B}[/tex]
