ap dung he thuc luong vao tam giac vuong ABD co AO vuong goc voi BD
\(AO^2=OB.OD\Rightarrow AO^2=8.18\Rightarrow AO=12\)
do AB song song voi CD ap dung he qua dl talet
\(\frac{AO}{OC}=\frac{OB}{OD}\Rightarrow OC=\frac{AO.OD}{OB}=\frac{14.18}{8}=31,5\)
SABCD=\(\frac{AC.BD}{2}=\frac{\left(14+31.5\right).\left(8+18\right)}{2}=591,5\)