[tex]a\in R \{ -1,1 \}\\\\\\\dfrac{2}{a+1} -\dfrac{1}{a-1} =\dfrac{2\cdot (a-1)-1\cdot (a+1)}{(a+1)\cdot (a-1)} =\dfrac{2a-2-a-1}{a^{2} -1} =\dfrac{a-3}{a^{2} -1} \\\\\\korzystam~~ze~~zworu~~skroconego~~mnozenia:\\\\(x-y)\cdot (x+y)=x^{2} -y^{2}\\\\Odp.~~A. \dfrac{a-3}{a^{2} -1}[/tex]
