Răspuns:
[tex]A = 165\text{ cm}^2[/tex]
Explicație pas cu pas:
[tex]DD'=33\text{ cm};\;AD = 4\text{ cm}\\\\P = 2AB + 2AD\\\Rightarrow18 = 2AB + 2\cdot4\Rightarrow\\\Rightarrow10 = 2AB\Rightarrow\\ \Rightarrow AB = 5\text{ cm}\\\\AB\parallel CD\text{ deci putem folosi formula ariei trapezului}\colon\\\\A = \frac{(AB + CD)\cdot DD'}{2} = & \frac{2AB\cdot DD'}{2}=AB\cdot DD'=5\cdot33 = 165\text{ cm}^2[/tex]
