[tex]\displaystyle\bf\\1)\\\\\frac{a^{2} -ab}{b^{2} -1} \cdot\frac{b+1}{a} =\frac{a\cdot(a-b)}{(b+1)\cdot(b-1)} \cdot\frac{b+1}{a} =\frac{a-b}{b-1} \\\\2)\\\\\frac{a-b}{b-1} -\frac{a}{b-1} =\frac{a-b-a}{b-1} =\frac{-b}{b-1} =\frac{b}{1-b}[/tex]