计算$\frac{1}{x-1}-\frac{1}{2\left( x-1 \right)}$的结果是 ．
$~~~~\frac{1}{x-1}-\frac{1}{2\left( x-1 \right)}$
$=\frac{2-1}{2\left( x-1 \right)}$
$=\frac{1}{2x-2}$．