# Find all points of discontinuity of the function $f(t)=\large\frac{1}{t^2+t-2},$where $\;t=\large\frac{1}{x-1}.$
$\begin{array}{1 1} 1,\frac{1}{2},2 \\ 1,\frac{-1}{2},2 \\ -1,\large\frac{1}{2},2 \\ -1,\large\frac{-1}{2},2 \end{array}$