19.如图,已知长方形ABCD四个顶点的坐标分别是$A(2, -2\sqrt{2}), B(5, -2\sqrt{2}), C(5, -\sqrt{2}), D(2, -\sqrt{2})$.
(1)求四边形ABCD的面积；
(2)将四边形ABCD向上平移$\sqrt{2}$个单位长度,求所得的四边形$A'B'C'D'$的四个顶点的坐标.

19.解:(1)四边形 ABCD 的面积为 $3 × (2\sqrt{2}-\sqrt{2})=3\sqrt{2}.$
(2)$A'(2,-\sqrt{2}),B'(5,-\sqrt{2}),C'(5,0),D'(2,0).$