$\frac{ \frac{ \mathrm{d} }{ \mathrm{d}x} \left( x+1 \right) \times \left( x-1 \right)-\left( x+1 \right) \times \frac{ \mathrm{d} }{ \mathrm{d}x} \left( x-1 \right) }{ {\left( x-1 \right)}^{2} }$
$\frac{ 1\left( x-1 \right)-\left( x+1 \right) \times \frac{ \mathrm{d} }{ \mathrm{d}x} \left( x-1 \right) }{ {\left( x-1 \right)}^{2} }$
$\frac{ 1\left( x-1 \right)-\left( x+1 \right) \times 1 }{ {\left( x-1 \right)}^{2} }$
$-\frac{ 2 }{ {\left( x-1 \right)}^{2} }$