Ans: C
$\begin{array}{cl}
& \dfrac{1}{x^2 -2x +1} – \dfrac{1}{x^2+x-2} \\
= & \dfrac{1}{(x-1)^2} – \dfrac{1}{(x-1)(x+2)} \\
= & \dfrac{(x+2)- (x-1)}{(x-1)^2(x+2)} \\
= & \dfrac{3}{(x-1)^2(x+2)}
\end{array}$
$\begin{array}{cl}
& \dfrac{1}{x^2 -2x +1} – \dfrac{1}{x^2+x-2} \\
= & \dfrac{1}{(x-1)^2} – \dfrac{1}{(x-1)(x+2)} \\
= & \dfrac{(x+2)- (x-1)}{(x-1)^2(x+2)} \\
= & \dfrac{3}{(x-1)^2(x+2)}
\end{array}$
