Biểu thức $\large\dfrac{1}{4}{x^2}{y^2} + xy + 1$ bằng: \(\large {\l

Biểu thức $\large\dfrac{1}{4}{x^2}{y^2} + xy + 1$ bằng:

• A.  $\large {\left( {\dfrac{1}{4}xy + 1} \right)^2}$
• B.  $\large {\left( {\dfrac{1}{2}xy + 1} \right)^2}$
• C. $\large {\left( {xy - \dfrac{1}{2}} \right)^2}$
• D. $\large {\left( {\dfrac{1}{2}xy - 1} \right)^2}$

$\large\dfrac{1}{4}{x^2}{y^2} + xy + 1={\left( {\dfrac{1}{2}xy} \right)^2} + 2.\dfrac{1}{2}xy + {1^2} ={\left( {\dfrac{1}{2}xy + 1} \right)^2}$