x2 – x + (frac{1}{4}) bằng:

A. \({\left( {x +\frac{1}{2}} \right)^2}\)

B. \({\left( {x - \frac{1}{2}} \right)^2}\)

C. \({\left( {x +\frac{1}{8}} \right)^2}\)

D. \({\left( {x +\frac{1}{4}} \right)^2}\)