Ans:
$$
\begin{array}{l}
(x-1)(2 x-1)=0 \\
\Rightarrow 2 x^{2}-x-2 x+1=0 \\
\Rightarrow 2 x^{2}-3 x+1=0 \\
\text { Here, } a=2, b=-3, c=1 \\
D=b^{2}-4 a c \\
=(-3)^{2}-4 \times 2 \times 1 \\
=9-8=1
\end{array}
$$