Tính diện tích hình thang ABCD biết widehat A = widehat
A.\({S_{ABCD}} = \frac{1}{2}\left( {12{x^2} - 3{y^2}} \right)\)
B.\({S_{ABCD}} = \frac{1}{2}\left( {12{x^2} + 6xy - 3{y^2}} \right)\)
C.\({S_{ABCD}} = \frac{1}{2}\left( {12{x^2} - 6xy - 3{y^2}} \right)\)
D.\({S_{ABCD}} = \frac{1}{2}\left( {12{x^2} -12xy+ 3{y^2}} \right)\)