$$\left. \begin{array} { l } { 2 } \\ { x ^ { 2 } - x + \frac { 1 } { 4 } } \\ { x ^ { 2 } - x + \frac { 1 } { 4 } } \end{array} \right.$$
$2,\ \frac{\left(2x-1\right)^{2}}{4},\ \frac{\left(2x-1\right)^{2}}{4}$
