Pomocí Greenovy vìty spoètìte
$\int \! \BBb F {d \vec \varphi} = \pm 27 / 4$, kde
$\Bbb F (x,y) = (3xy, 2x^2)$ a $\varphi$ je obvod
$A = \{(x,y) \in \Bbb R ^2, x^2 - 2x < y < x 
\}$.
