Do : \(\left(x-\dfrac{1}{2}\right)^2\ge0\Rightarrow-\left(x-\dfrac{1}{2}\right)^2\le0\Rightarrow-\left(x-\dfrac{1}{2}\right)^2+\dfrac{1}{4}\le\dfrac{1}{4}\)
Vậy GTLN của N là \(\dfrac{1}{4}\) . Dấu \("="\) xảy ra khi \(x-\dfrac{1}{2}=0\Leftrightarrow x=\dfrac{1}{2}\)
