0} \atop {5,\; pri\; a<0}} \right. ,\; a\ne 0\\\\\frac{2|a-1|}{a-1}= \left \{ {{-2,\; pri \; a<1} \atop {2,\; pri \; a>1}} \right. ,\; a\ne 1" alt="9)\; \; \frac{a^2-b^2}{a^2+b^2},\; a\in R,\; b\in R\\\\\frac{1-b}{|b|}\,\; b\ne 0,\; b\in (-\infty,0)U(0,+\infty)\\\\\frac{9}{a^2-9},\; a\ne \pm 3,\; a\in (-\infty,-3)U(-3,3)U(3,+\infty)\\\\10)\; \; \frac{5a}{|a|}= \left \{ {{-5,pri\; a>0} \atop {5,\; pri\; a<0}} \right. ,\; a\ne 0\\\\\frac{2|a-1|}{a-1}= \left \{ {{-2,\; pri \; a<1} \atop {2,\; pri \; a>1}} \right. ,\; a\ne 1" align="absmiddle" class="latex-formula">