a, \(S_{ABCD}=12\times6=72\left(cm^2\right)\)
b,Ta có: DE=DC-EC=12-9=3(cm)
\(S_{ADE}=\dfrac{6\times3}{2}=9\left(cm^2\right)\)
\(S_{ABCE}=\dfrac{\left(12+9\right)\times6}{2}=63\left(cm^2\right)\)
\(\dfrac{S_{ADE}}{S_{ABCE}}=\dfrac{9}{63}=\dfrac{1}{7}\)
a, SABCD=12×6=72(cm2)
b,Ta có: DE=DC-EC=12-9=3(cm)
SABCE=(12+9)×62=63(cm2)